Method and device for signaling information relating to slice type in picture header in image/video coding system

ABSTRACT

A video decoding method performed by a video decoding device according to the present document may comprise the steps of: acquiring image information from a bitstream, wherein the image information includes a picture header associated with a current picture, and the current picture includes multiple slices; based on the picture header, acquiring at least one of a first flag indicating whether information required for an inter-prediction operation exists in the picture header and a second flag indicating whether information required for an intra-prediction operation exists in the picture header; based on at least one of the first flag and the second flag, generating prediction samples.

This application is a Continuation Application of InternationalApplication No. PCT/KR2020/015401, filed on Nov. 5, 2020, which claimsthe benefit of U.S. Provisional Application No. 62/931,165, filed onNov. 5, 2019, the contents of which are all hereby incorporated byreference herein in their entirety.

BACKGROUND OF DISCLOSURE Field of the Disclosure

The present disclosure relates to a method and apparatus for signalinginformation relating to a slice type in a picture header in animage/video coding system.

Related Art

Recently, the demand for high resolution, high quality image/video suchas 4K, 8K or more Ultra High Definition (UHD) image/video is increasingin various fields. As the image/video resolution or quality becomeshigher, relatively more amount of information or bits are transmittedthan for conventional image/video data. Therefore, if image/video dataare transmitted via a medium such as an existing wired/wirelessbroadband line or stored in a legacy storage medium, costs fortransmission and storage are readily increased.

Moreover, interests and demand are growing for virtual reality (VR) andartificial reality (AR) contents, and immersive media such as hologram;and broadcasting of images/videos exhibiting image/video characteristicsdifferent from those of an actual image/video, such as gameimages/videos, are also growing.

Therefore, a highly efficient image/video compression technique isrequired to effectively compress and transmit, store, or play highresolution, high quality images/videos showing various characteristicsas described above.

SUMMARY

This document is to provide a method and apparatus for improvingimage/video coding efficiency.

This document is also to provide a method and apparatus for efficientlyperforming inter prediction and/or intra prediction in image/videocoding.

This document is also to provide a method and apparatus for efficientlysignaling slice type related information in transmitting image/videoinformation.

This document is also to provide a method and apparatus for omittingunnecessary information in image/video coding.

This document is also to provide a method and apparatus for preventingsignaling unnecessary for inter prediction and/or intra prediction intransmitting image/video information.

This document is also to provide a method and apparatus for signalinginformation about a slice type in a picture header in coding animage/video.

According to an embodiment of this document, a video decoding methodperformed by a video decoding apparatus is provided, the methodincluding: obtaining image information from a bitstream, wherein theimage information includes a picture header associated with a currentpicture, and the current picture includes a plurality of slices;obtaining, based on the picture header, at least one of a first flagindicating whether information necessary for an inter predictionoperation is present in the picture header or a second flag indicatingwhether information necessary for an intra prediction operation ispresent in the picture header; generating prediction samples byperforming at least one of intra prediction or inter prediction on acurrent block in the current picture based on at least one of the firstflag or the second flag; generating residual samples based on residualinformation obtained from the image information; and generatingreconstructed samples based on the prediction samples and the residualsamples.

According to another embodiment of this document, a video encodingmethod performed by a video encoding apparatus is provided, the methodincluding: generating prediction samples for a current block in acurrent picture based on a prediction mode of the current block in thecurrent picture, wherein the current picture includes a plurality ofslices; generating, based on the prediction mode, at least one of firstinformation indicating whether information necessary for an interprediction operation is present in a picture header associated with thecurrent picture or second information indicating whether informationnecessary for an intra prediction operation is present in the pictureheader; generating residual information based on the prediction samplesand an original picture; and encoding image information including atleast one of the first information or the second information and theresidual information, wherein the first information and the secondinformation are included in the picture header of the image information.

According to still another embodiment of this document, there isprovided a computer-readable digital storage medium containinginformation which causes a decoding apparatus to perform a videodecoding method, the decoding method including: obtaining imageinformation, wherein the image information includes a picture headerassociated with a current picture, and the current picture includes aplurality of slices; obtaining, based on the picture header, at leastone of a first flag indicating whether information necessary for aninter prediction operation is present in the picture header or a secondflag indicating whether information necessary for an intra predictionoperation is present in the picture header; generating predictionsamples by performing at least one of intra prediction or interprediction on a current block in the current picture based on at leastone of the first flag or the second flag; generating residual samplesbased on residual information obtained from the image information; andgenerating reconstructed samples based on the prediction samples and theresidual samples.

According to an embodiment of the present document, it is possible toimprove overall image/video compression efficiency.

According to an embodiment of this document, it is possible to performinter prediction and/or intra prediction efficiently when coding animage/video.

According to an embodiment of this document, it is possible to signalinformation related to a slice type efficiently when transmittingimage/video information.

According to an embodiment of this document, it is possible to omitunnecessary information when coding an image/video.

According to an embodiment of this document, it is possible to preventthe signaling of syntax elements unnecessary for inter prediction orintra prediction when transmitting image/video information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example of a video/image coding system towhich embodiments of the present disclosure may be applied.

FIG. 2 is a diagram schematically illustrating a configuration of avideo/image encoding apparatus to which embodiments of the presentdisclosure may be applied.

FIG. 3 is a diagram schematically illustrating a configuration of avideo/image decoding apparatus to which embodiments of the presentdisclosure may be applied.

FIG. 4 represents an example of an entropy encoding method.

FIG. 5 represents an example of an entropy decoding method.

FIG. 6 represents an example of a picture decoding process.

FIG. 7 represents an example of a picture encoding process.

FIG. 8 represents an example of an inter prediction based video/imagedecoding method.

FIG. 9 represents an example of an inter prediction based video/imagedecoding method.

FIGS. 10 and 11 schematically represent an example of a video/imageencoding method and associated components according to an embodiment ofthis document.

FIGS. 12 and 13 schematically represent an example of a video/imagedecoding method and associated components according to an embodiment ofthis document.

FIG. 14 shows an example of a contents streaming system to whichembodiments disclosed in this document may be applied.

DESCRIPTION OF EMBODIMENTS

This document relates to video/image coding. For example, amethod/embodiment disclosed in this document may be applied to a methoddisclosed in a versatile video coding (VVC) standard. In addition, themethod/embodiment disclosed in this document may be applied to a methoddisclosed in an essential video coding (EVC) standard, AOMedia Video 1(AV1) standard, 2nd generation of audio video coding standard (AVS2), ora next-generation video/image coding standard (e.g., H.267, H.268,etc.).

Various embodiments related to video/image coding are presented in thisdocument, and the embodiments may be combined with each other unlessotherwise stated.

In this document, the term “/” and “,” should be interpreted to indicate“and/or.” For instance, the expression “A/B” may mean “A and/or B.”Further, “A, B” may mean “A and/or B.” Further, “A/B/C” may mean “atleast one of A, B, and/or C.” Also, “A/B/C” may mean “at least one of A,B, and/or C.

“Further, in the document, the term “or” should be interpreted toindicate “and/or.” For instance, the expression “A or B” may comprise 1)only A, 2) only B, and/or 3) both A and B. In other words, the term “or”in this document should be interpreted to indicate “additionally oralternatively.”

Further, the parentheses used in the present specification may mean “forexample”. Specifically, in the case that “prediction (intra prediction)”is expressed, it may be indicated that “intra prediction” is proposed asan example of “prediction”. In other words, the term “prediction” in thepresent specification is not limited to “intra prediction”, and it maybe indicated that “intra prediction” is proposed as an example of“prediction”. Further, even in the case that “prediction (i.e., intraprediction)” is expressed, it may be indicated that “intra prediction”is proposed as an example of “prediction”.

The disclosure of the present document may be modified in various forms,and specific embodiments thereof will be described and illustrated inthe drawings. The terms used in the present disclosure are used tomerely describe specific embodiments, but are not intended to limit thedisclosed method in the present disclosure. An expression of a singularnumber includes an expression of ‘at least one’, so long as it isclearly read differently. The terms such as “include” and “have” areintended to indicate that features, numbers, steps, operations,elements, components, or combinations thereof used in the document existand it should be thus understood that the possibility of existence oraddition of one or more different features, numbers, steps, operations,elements, components, or combinations thereof is not excluded.

In addition, each configuration of the drawings described in thisdocument is an independent illustration for explaining functions asfeatures that are different from each other, and does not mean that eachconfiguration is implemented by mutually different hardware or differentsoftware. For example, two or more of the configurations may be combinedto form one configuration, and one configuration may also be dividedinto multiple configurations. Without departing from the gist of thedisclosed method of the present document, embodiments in whichconfigurations are combined and/or separated are included in the scopeof the disclosure of the present document.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In addition, likereference numerals are used to indicate like elements throughout thedrawings, and the same descriptions on the like elements may be omitted.

FIG. 1 illustrates an example of a video/image coding system to whichthe embodiments of the present disclosure may be applied.

Referring to FIG. 1 , a video/image coding system may include a firstdevice (a source device) and a second device (a reception device). Thesource device may transmit encoded video/image information or data tothe reception device through a digital storage medium or network in theform of a file or streaming.

The source device may include a video source, an encoding apparatus, anda transmitter. The receiving device may include a receiver, a decodingapparatus, and a renderer. The encoding apparatus may be called avideo/image encoding apparatus, and the decoding apparatus may be calleda video/image decoding apparatus. The transmitter may be included in theencoding apparatus. The receiver may be included in the decodingapparatus. The renderer may include a display, and the display may beconfigured as a separate device or an external component.

The video source may acquire video/image through a process of capturing,synthesizing, or generating the video/image. The video source mayinclude a video/image capture device and/or a video/image generatingdevice. The video/image capture device may include, for example, one ormore cameras, video/image archives including previously capturedvideo/images, and the like. The video/image generating device mayinclude, for example, computers, tablets and smartphones, and may(electronically) generate video/images. For example, a virtualvideo/image may be generated through a computer or the like. In thiscase, the video/image capturing process may be replaced by a process ofgenerating related data.

The encoding apparatus may encode input video/image. The encodingapparatus may perform a series of procedures such as prediction,transform, and quantization for compaction and coding efficiency. Theencoded data (encoded video/image information) may be output in the formof a bitstream.

The transmitter may transmit the encoded image/image information or dataoutput in the form of a bitstream to the receiver of the receivingdevice through a digital storage medium or a network in the form of afile or streaming. The digital storage medium may include variousstorage mediums such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and thelike. The transmitter may include an element for generating a media filethrough a predetermined file format and may include an element fortransmission through a broadcast/communication network. The receiver mayreceive/extract the bitstream and transmit the received bitstream to thedecoding apparatus.

The decoding apparatus may decode the video/image by performing a seriesof procedures such as dequantization, inverse transform, and predictioncorresponding to the operation of the encoding apparatus.

The renderer may render the decoded video/image. The renderedvideo/image may be displayed through the display.

In this document, a video may refer to a series of images over time. Apicture generally refers to the unit representing one image at aparticular time frame, and a slice/tile refers to the unit constitutinga part of the picture in terms of coding. A slice/tile may include oneor more coding tree units (CTUs). One picture may consist of one or moreslices/tiles. One picture may consist of one or more tile groups. Onetile group may include one or more tiles. A brick may represent arectangular region of CTU rows within a tile in a picture). A tile maybe partitioned into multiple bricks, each of which consisting of one ormore CTU rows within the tile. A tile that is not partitioned intomultiple bricks may be also referred to as a brick. A brick scan is aspecific sequential ordering of CTUs partitioning a picture in which theCTUs are ordered consecutively in CTU raster scan in a brick, brickswithin a tile are ordered consecutively in a raster scan of the bricksof the tile, and tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A tile is a rectangular regionof CTUs within a particular tile column and a particular tile row in apicture. The tile column is a rectangular region of CTUs having a heightequal to the height of the picture and a width specified by syntaxelements in the picture parameter set. The tile row is a rectangularregion of CTUs having a height specified by syntax elements in thepicture parameter set and a width equal to the width of the picture). Atile scan is a specific sequential ordering of CTUs partitioning apicture in which the CTUs are ordered consecutively in CTU raster scanin a tile whereas tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A slice includes an integernumber of bricks of a picture that may be exclusively contained in asingle NAL unit. A slice may consists of either a number of completetiles or only a consecutive sequence of complete bricks of one tile. Inthis document, tile group and slice may be used interchangeably. Forexample, in this document, a tile group/tile group header may bereferred to as a slice/slice header.

A pixel or a pel may mean a smallest unit constituting one picture (orimage). Also, ‘sample’ may be used as a term corresponding to a pixel. Asample may generally represent a pixel or a value of a pixel, and mayrepresent only a pixel/pixel value of a luma component or only apixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit mayinclude at least one of a specific region of the picture and informationrelated to the region. One unit may include one luma block and twochroma (ex. Cb, cr) blocks. The unit may be used interchangeably withterms such as block or area in some cases. In a general case, an M×Nblock may include samples (or sample arrays) or a set (or array) oftransform coefficients of M columns and N rows. Alternatively, thesample may mean a pixel value in the spatial domain, and when such apixel value is transformed to the frequency domain, it may mean atransform coefficient in the frequency domain.

The unit may be interchangeably used with the term such as a block or anarea in some cases. Generally, an M×N block may represent samplescomposed of M columns and N rows or a group of transform coefficients.The sample may generally represent a pixel or a value of the pixel, andmay also represent only the pixel/pixel value of a luma component, andalso represent only the pixel/pixel value of a chroma component. Thesample may be used as the term corresponding to a pixel or a pelconfiguring one picture (or image).

FIG. 2 is a diagram schematically illustrating the configuration of avideo/image encoding apparatus to which the embodiments of the presentdisclosure may be applied. Hereinafter, what is referred to as the videoencoding apparatus may include an image encoding apparatus.

Referring to FIG. 2 , the encoding apparatus 200 may include and beconfigured with an image partitioner 210, a predictor 220, a residualprocessor 230, an entropy encoder 240, an adder 250, a filter 260, and amemory 270. The predictor 220 may include an inter predictor 221 and anintra predictor 222. The residual processor 230 may include atransformer 232, a quantizer 233, a dequantizer 234, and an inversetransformer 235. The residual processor 230 may further include asubtractor 231. The adder 250 may be called a reconstructor orreconstructed block generator. The image partitioner 210, the predictor220, the residual processor 230, the entropy encoder 240, the adder 250,and the filter 260, which have been described above, may be configuredby one or more hardware components (e.g., encoder chipsets orprocessors) according to an embodiment. In addition, the memory 270 mayinclude a decoded picture buffer (DPB), and may also be configured by adigital storage medium. The hardware component may further include thememory 270 as an internal/external component.

The image partitioner 210 may split an input image (or, picture, frame)input to the encoding apparatus 200 into one or more processing units.As an example, the processing unit may be called a coding unit (CU). Inthis case, the coding unit may be recursively split according to aQuad-tree binary-tree ternary-tree (QTBTTT) structure from a coding treeunit (CTU) or the largest coding unit (LCU). For example, one codingunit may be split into a plurality of coding units of a deeper depthbased on a quad-tree structure, a binary-tree structure, and/or aternary-tree structure. In this case, for example, the quad-treestructure is first applied and the binary-tree structure and/or theternary-tree structure may be later applied. Alternatively, thebinary-tree structure may also be first applied. A coding procedureaccording to the present disclosure may be performed based on a finalcoding unit which is not split any more. In this case, based on codingefficiency according to image characteristics or the like, the maximumcoding unit may be directly used as the final coding unit, or asnecessary, the coding unit may be recursively split into coding units ofa deeper depth, such that a coding unit having an optimal size may beused as the final coding unit. Here, the coding procedure may include aprocedure such as prediction, transform, and reconstruction to bedescribed later. As another example, the processing unit may furtherinclude a prediction unit (PU) or a transform unit (TU). In this case,each of the prediction unit and the transform unit may be split orpartitioned from the aforementioned final coding unit. The predictionunit may be a unit of sample prediction, and the transform unit may be aunit for inducing a transform coefficient and/or a unit for inducing aresidual signal from the transform coefficient.

The encoding apparatus 200 may subtract the prediction signal (predictedblock, prediction sample array) output from the inter predictor 221 orthe intra predictor 222 from the input image signal (original block,original sample array) to generate a residual signal (residual block,residual sample array), and the generated residual signal is transmittedto the transformer 232. In this case, as illustrated, a unit forsubtracting the prediction signal (prediction block, prediction samplearray) from an input image signal (original block, original samplearray) in the encoder 200 may be referred to as a subtractor 231. Thepredictor 220 may perform prediction on a processing target block(hereinafter, referred to as a current block) and generate a predictedblock including prediction samples for the current block. The predictor220 may determine whether intra prediction or inter prediction isapplied in units of a current block or CU. The predictor 220 maygenerate various information on prediction, such as prediction modeinformation, and transmit the generated information to the entropyencoder 240, as is described below in the description of each predictionmode. The information on prediction may be encoded by the entropyencoder 240 and output in the form of a bitstream.

The intra predictor 222 may predict a current block with reference tosamples within a current picture. The referenced samples may be locatedneighboring to the current block, or may also be located away from thecurrent block according to the prediction mode. The prediction modes inthe intra prediction may include a plurality of non-directional modesand a plurality of directional modes. The non-directional mode mayinclude, for example, a DC mode or a planar mode. The directional modemay include, for example, 33 directional prediction modes or 65directional prediction modes according to the fine degree of theprediction direction. However, this is illustrative and the directionalprediction modes which are more or less than the above number may beused according to the setting. The intra predictor 222 may alsodetermine the prediction mode applied to the current block using theprediction mode applied to the neighboring block.

The inter predictor 221 may induce a predicted block of the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. At this time, in order to decreasethe amount of motion information transmitted in the inter predictionmode, the motion information may be predicted in units of a block, asub-block, or a sample based on the correlation of the motioninformation between the neighboring block and the current block. Themotion information may include a motion vector and a reference pictureindex. The motion information may further include inter predictiondirection (L0 prediction, L1 prediction, Bi prediction, or the like)information. In the case of the inter prediction, the neighboring blockmay include a spatial neighboring block existing within the currentpicture and a temporal neighboring block existing in the referencepicture. The reference picture including the reference block and thereference picture including the temporal neighboring block may also bethe same as each other, and may also be different from each other. Thetemporal neighboring block may be called the name such as a collocatedreference block, a collocated CU (colCU), or the like, and the referencepicture including the temporal neighboring block may also be called acollocated picture (colPic). For example, the inter predictor 221 mayconfigure a motion information candidate list based on the neighboringblocks, and generate information indicating what candidate is used toderive the motion vector and/or the reference picture index of thecurrent block. The inter prediction may be performed based on variousprediction modes, and for example, in the case of a skip mode and amerge mode, the inter predictor 221 may use the motion information ofthe neighboring block as the motion information of the current block. Inthe case of the skip mode, the residual signal may not be transmittedunlike the merge mode. A motion vector prediction (MVP) mode mayindicate the motion vector of the current block by using the motionvector of the neighboring block as a motion vector predictor, andsignaling a motion vector difference.

The predictor 220 may generate a prediction signal based on variousprediction methods to be described below. For example, the predictor 220may apply intra prediction or inter prediction for prediction of oneblock and may simultaneously apply intra prediction and interprediction. This may be called combined inter and intra prediction(CIIP). In addition, the predictor may be based on an intra block copy(IBC) prediction mode or based on a palette mode for prediction of ablock. The IBC prediction mode or the palette mode may be used forimage/video coding of content such as games, for example, screen contentcoding (SCC). IBC basically performs prediction within the currentpicture, but may be performed similarly to inter prediction in that areference block is derived within the current picture. That is, IBC mayuse at least one of the inter prediction techniques described in thisdocument. The palette mode may be viewed as an example of intra codingor intra prediction. When the palette mode is applied, a sample value inthe picture may be signaled based on information on the palette tableand the palette index.

The prediction signal generated by the predictor (including the interpredictor 221 and/or the intra predictor 222) may be used to generate areconstructed signal or may be used to generate a residual signal.

The transformer 232 may generate transform coefficients by applying atransform technique to the residual signal. For example, the transformtechnique may include at least one of a discrete cosine transform (DCT),a discrete sine transform (DST), a graph-based transform (GBT), or aconditionally non-linear transform (CNT). Here, GBT refers totransformation obtained from a graph when expressing relationshipinformation between pixels in the graph. CNT refers to transformationobtained based on a prediction signal generated using all previouslyreconstructed pixels. Also, the transformation process may be applied toa block of pixels having the same size as a square or may be applied toa block of a variable size that is not a square.

The quantizer 233 quantizes the transform coefficients and transmits thesame to the entropy encoder 240, and the entropy encoder 240 encodes thequantized signal (information on the quantized transform coefficients)and outputs the encoded signal as a bitstream. Information on thequantized transform coefficients may be referred to as residualinformation. The quantizer 233 may rearrange the quantized transformcoefficients in the block form into a one-dimensional vector form basedon a coefficient scan order and may generate information on thetransform coefficients based on the quantized transform coefficients inthe one-dimensional vector form.

The entropy encoder 240 may perform various encoding methods such as,for example, exponential Golomb, context-adaptive variable length coding(CAVLC), and context-adaptive binary arithmetic coding (CABAC). Theentropy encoder 240 may encode information necessary for video/imagereconstruction (e.g., values of syntax elements, etc.) other than thequantized transform coefficients together or separately. Encodedinformation (e.g., encoded video/image information) may be transmittedor stored in units of a network abstraction layer (NAL) unit in the formof a bitstream. The video/image information may further includeinformation on various parameter sets, such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). Also, the video/image informationmay further include general constraint information. In this document,information and/or syntax elements transmitted/signaled from theencoding apparatus to the decoding apparatus may be included invideo/image information. The video/image information may be encodedthrough the encoding procedure described above and included in thebitstream. The bitstream may be transmitted through a network or may bestored in a digital storage medium. Here, the network may include abroadcasting network and/or a communication network, and the digitalstorage medium may include various storage media such as USB, SD, CD,DVD, Blu-ray, HDD, and SSD. A transmitting unit (not shown) and/or astoring unit (not shown) for transmitting or storing a signal outputfrom the entropy encoder 240 may be configured as internal/externalelements of the encoding apparatus 200, or the transmitting unit may beincluded in the entropy encoder 240.

The quantized transform coefficients output from the quantizer 233 maybe used to generate a prediction signal. For example, the residualsignal (residual block or residual samples) may be reconstructed byapplying dequantization and inverse transform to the quantized transformcoefficients through the dequantizer 234 and the inverse transform unit235. The adder 250 may add the reconstructed residual signal to theprediction signal output from the inter predictor 221 or the intrapredictor 222 to generate a reconstructed signal (reconstructed picture,reconstructed block, reconstructed sample array). When there is noresidual for the processing target block, such as when the skip mode isapplied, the predicted block may be used as a reconstructed block. Theadder 250 may be referred to as a restoration unit or a restorationblock generator. The generated reconstructed signal may be used forintra prediction of a next processing target block in the currentpicture, or may be used for inter prediction of the next picture afterbeing filtered as described below.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied duringa picture encoding and/or reconstruction process.

The filter 260 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter260 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture, and store the modifiedreconstructed picture in the memory 270, specifically, in a DPB of thememory 270. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like. The filter 260 may generate variouskinds of information related to the filtering, and transfer thegenerated information to the entropy encoder 240 as described later inthe description of each filtering method. The information related to thefiltering may be encoded by the entropy encoder 240 and output in theform of a bitstream.

The modified reconstructed picture transmitted to the memory 270 may beused as a reference picture in the inter predictor 221. When the interprediction is applied through the encoding apparatus, predictionmismatch between the encoding apparatus 200 and the decoding apparatusmay be avoided and encoding efficiency may be improved.

The DPB of the memory 270 may store the modified reconstructed picturefor use as the reference picture in the inter predictor 221. The memory270 may store motion information of a block from which the motioninformation in the current picture is derived (or encoded) and/or motioninformation of blocks in the picture, having already been reconstructed.The stored motion information may be transferred to the inter predictor221 to be utilized as motion information of the spatial neighboringblock or motion information of the temporal neighboring block. Thememory 270 may store reconstructed samples of reconstructed blocks inthe current picture, and may transfer the reconstructed samples to theintra predictor 222.

FIG. 3 is a diagram for schematically explaining the configuration of avideo/image decoding apparatus to which the embodiments of the presentdisclosure may be applied.

Referring to FIG. 3 , the decoding apparatus 300 may include andconfigured with an entropy decoder 310, a residual processor 320, apredictor 330, an adder 340, a filter 350, and a memory 360. Thepredictor 330 may include an inter predictor 331 and an intra predictor332. The residual processor 320 may include a dequantizer 321 and aninverse transformer 322. The entropy decoder 310, the residual processor320, the predictor 330, the adder 340, and the filter 350, which havebeen described above, may be configured by one or more hardwarecomponents (e.g., decoder chipsets or processors) according to anembodiment. Further, the memory 360 may include a decoded picture buffer(DPB), and may be configured by a digital storage medium. The hardwarecomponent may further include the memory 360 as an internal/externalcomponent.

When the bitstream including the video/image information is input, thedecoding apparatus 300 may reconstruct the image in response to aprocess in which the video/image information is processed in theencoding apparatus illustrated in FIG. 2 . For example, the decodingapparatus 300 may derive the units/blocks based on block split-relatedinformation acquired from the bitstream. The decoding apparatus 300 mayperform decoding using the processing unit applied to the encodingapparatus. Therefore, the processing unit for the decoding may be, forexample, a coding unit, and the coding unit may be split according tothe quad-tree structure, the binary-tree structure, and/or theternary-tree structure from the coding tree unit or the maximum codingunit. One or more transform units may be derived from the coding unit.In addition, the reconstructed image signal decoded and output throughthe decoding apparatus 300 may be reproduced through a reproducingapparatus.

The decoding apparatus 300 may receive a signal output from the encodingapparatus of FIG. 2 in the form of a bitstream, and the received signalmay be decoded through the entropy decoder 310. For example, the entropydecoder 310 may parse the bitstream to derive information (e.g.,video/image information) necessary for image reconstruction (or picturereconstruction). The video/image information may further includeinformation on various parameter sets such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). In addition, the video/imageinformation may further include general constraint information. Thedecoding apparatus may further decode picture based on the informationon the parameter set and/or the general constraint information.Signaled/received information and/or syntax elements described later inthis document may be decoded may decode the decoding procedure andobtained from the bitstream. For example, the entropy decoder 310decodes the information in the bitstream based on a coding method suchas exponential Golomb coding, context-adaptive variable length coding(CAVLC), or context-adaptive arithmetic coding (CABAC), and outputsyntax elements required for image reconstruction and quantized valuesof transform coefficients for residual. More specifically, the CAB ACentropy decoding method may receive a bin corresponding to each syntaxelement in the bitstream, determine a context model by using a decodingtarget syntax element information, decoding information of a decodingtarget block or information of a symbol/bin decoded in a previous stage,and perform an arithmetic decoding on the bin by predicting aprobability of occurrence of a bin according to the determined contextmodel, and generate a symbol corresponding to the value of each syntaxelement. In this case, the CABAC entropy decoding method may update thecontext model by using the information of the decoded symbol/bin for acontext model of a next symbol/bin after determining the context model.The information related to the prediction among the information decodedby the entropy decoder 310 may be provided to the the predictor (interpredictor 332 and intra predictor 331), and residual values on which theentropy decoding has been performed in the entropy decoder 310, that is,the quantized transform coefficients and related parameter information,may be input to the residual processor 320.

The residual processor 320 may derive a residual signal (residual block,residual samples, residual sample array). Also, information on filteringamong the information decoded by the entropy decoder 310 may be providedto the filter 350. Meanwhile, a receiving unit (not shown) for receivinga signal output from the encoding apparatus may be further configured asan internal/external element of the decoding apparatus 300, or thereceiving unit may be a component of the entropy decoder 310. Meanwhile,the decoding apparatus according to this document may be called avideo/image/picture decoding apparatus, and the decoding apparatus maybe divided into an information decoder (video/image/picture informationdecoder) and a sample decoder (video/image/picture sample decoder). Theinformation decoder may include the entropy decoder 310, and the sampledecoder may include at least one of the dequantizer 321, the inversetransformer 322, the adder 340, the filter 350, the memory 360, an interpredictor 332, and an intra predictor 331.

The dequantizer 321 may dequantize the quantized transform coefficientsto output the transform coefficients. The dequantizer 321 may rearrangethe quantized transform coefficients in a two-dimensional block form. Inthis case, the rearrangement may be performed based on a coefficientscan order performed by the encoding apparatus. The dequantizer 321 mayperform dequantization for the quantized transform coefficients using aquantization parameter (e.g., quantization step size information), andacquire the transform coefficients.

The inverse transformer 322 inversely transforms the transformcoefficients to acquire the residual signal (residual block, residualsample array).

The predictor 330 may perform the prediction of the current block, andgenerate a predicted block including the prediction samples of thecurrent block. The predictor may determine whether the intra predictionis applied or the inter prediction is applied to the current block basedon the information on prediction output from the entropy decoder 310,and determine a specific intra/inter prediction mode.

The predictor 330 may generate a prediction signal based on variousprediction methods to be described later. For example, the predictor mayapply intra prediction or inter prediction for prediction of one block,and may simultaneously apply intra prediction and inter prediction. Thismay be called combined inter and intra prediction (CIIP). In addition,the predictor may be based on an intra block copy (IBC) prediction modeor based on a palette mode for prediction of a block. The IBC predictionmode or the palette mode may be used for image/video coding of contentsuch as games, for example, screen content coding (SCC). IBC maybasically perform prediction within the current picture, but may beperformed similarly to inter prediction in that a reference block isderived within the current picture. That is, IBC may use at least one ofthe inter prediction techniques described in this document. The palettemode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, information on the palettetable and the palette index may be included in the video/imageinformation and signaled.

The intra predictor 331 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block, or may be located apart fromthe current block according to the prediction mode. In intra prediction,prediction modes may include a plurality of non-directional modes and aplurality of directional modes. The intra predictor 331 may determinethe prediction mode to be applied to the current block by using theprediction mode applied to the neighboring block.

The inter predictor 332 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. In this case, in order to reducethe amount of motion information being transmitted in the interprediction mode, motion information may be predicted in the unit ofblocks, subblocks, or samples based on correlation of motion informationbetween the neighboring block and the current block. The motioninformation may include a motion vector and a reference picture index.The motion information may further include information on interprediction direction (L0 prediction, L1 prediction, Bi prediction, andthe like). In case of inter prediction, the neighboring block mayinclude a spatial neighboring block existing in the current picture anda temporal neighboring block existing in the reference picture. Forexample, the inter predictor 332 may construct a motion informationcandidate list based on neighboring blocks, and derive a motion vectorof the current block and/or a reference picture index based on thereceived candidate selection information. Inter prediction may beperformed based on various prediction modes, and the information on theprediction may include information indicating a mode of inter predictionfor the current block.

The adder 340 may generate a reconstructed signal (reconstructedpicture, reconstructed block, or reconstructed sample array) by addingthe obtained residual signal to the prediction signal (predicted blockor predicted sample array) output from the predictor (including interpredictor 332 and/or intra predictor 331). If there is no residual forthe processing target block, such as a case that a skip mode is applied,the predicted block may be used as the reconstructed block.

The adder 340 may be called a reconstructor or a reconstructed blockgenerator. The generated reconstructed signal may be used for the intraprediction of a next block to be processed in the current picture, andas described later, may also be output through filtering or may also beused for the inter prediction of a next picture.

Meanwhile, a luma mapping with chroma scaling (LMCS) may also be appliedin the picture decoding process.

The filter 350 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter350 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture, and store the modifiedreconstructed picture in the memory 360, specifically, in a DPB of thememory 360. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360may be used as a reference picture in the inter predictor 332. Thememory 360 may store the motion information of the block from which themotion information in the current picture is derived (or decoded) and/orthe motion information of the blocks in the picture having already beenreconstructed. The stored motion information may be transferred to theinter predictor 332 so as to be utilized as the motion information ofthe spatial neighboring block or the motion information of the temporalneighboring block. The memory 360 may store reconstructed samples ofreconstructed blocks in the current picture, and transfer thereconstructed samples to the intra predictor 331.

In the present document, the embodiments described in the filter 260,the inter predictor 221, and the intra predictor 222 of the encodingapparatus 200 may be applied equally or to correspond to the filter 350,the inter predictor 332, and the intra predictor 331.

The video/image coding method according to the present document may beperformed based on the following partitioning structure. Specifically,procedures of prediction, residual processing ((inverse) transform and(de)quantization), syntax element coding, and filtering to be describedlater may be performed based on CTU and CU (and/or TU and PU) derivedbased on the partitioning structure. A block partitioning procedure maybe performed by the image partitioner 210 of the above-describedencoding apparatus, and partitioning related information may beprocessed (encoded) by the entropy encoder 240, and may be transferredto the decoding apparatus in the form of a bitstream. The entropydecoder 310 of the decoding apparatus may derive the block partitioningstructure of the current picture based on the partitioning relatedinformation obtained from the bitstream, and based on this, may performa series of procedures for image decoding (e.g., prediction, residualprocessing, block/picture reconstruction, and in-loop filtering). The CUsize and the TU size may be equal to each other, or a plurality of TUsmay be present in the CU area. Meanwhile, the CU size may generallyrepresent a luma component (sample) coding block (CB) size. The TU sizemay generally represent a luma component (sample) transform block (TB)size. A chroma component (sample) CB or TB size may be derived based onthe luma component (sample) CB or TB size in accordance with a componentratio according to a color format (chroma format, e.g., 4:4:4, 4:2:2,4:2:0, and the like) of the picture/image. The TU size may be derivedbased on maxTbSize. For example, if the CU size is larger than themaxTbSize, a plurality of TUs (TBs) of the maxTbSize may be derived, andthe transform/inverse transform may be performed in the unit of the TU(TB). Further, for example, in case that intra prediction is applied,the intra prediction mode/type may be derived in the unit of CU (or CB),and the derivation of a neighboring reference sample and the generationof a prediction sample may be performed in the unit of TU (or TB). Inthis case, one or a plurality of TUs (or TBs) may be present in one CU(or CB) area, and in this case, the plurality of TUs (or TBs) may sharethe same intra prediction mode/type.

Further, in coding the video/image according to the present document,the image processing unit may have a hierarchical structure. One picturemay be divided into one or more tiles, bricks, slices, and/or tilegroups. One slice may include one or more bricks. One brick may includeone or more CTU rows in a tile. The slice may include an integer numberof bricks of the picture. One tile group may include one or more tiles.One tile is a rectangular region of CTUs within a particular tile columnand a particular tile row in a picture. The tile group may include aninteger number of tiles in accordance with the tile raster scan in thepicture. A slice header may carry information/parameters that can beapplied to the corresponding slice (blocks in the slice). In case thatthe encoding/decoding apparatus has a multi-core processor, theencoding/decoding procedures for the tile, slice, brick, and/or tilegroup may be processed in parallel. In the present document, the sliceor the tile group may be interchangeably used. That is, the tile groupheader may be called a slice header. Here, the slice may have one ofslice types including an intra (I) slice, a predictive (P) slice, and abi-predictive (B) slice. For prediction of blocks in I slice, the interprediction may not be used, but only the intra prediction may be used.Even in this case, the original sample value may be coded and signaledwithout the prediction. For blocks in the P slice, the intra predictionor the inter prediction may be used, and in case of using the interprediction, only uni-prediction may be used. Meanwhile, for blocks inthe B slice, the intra prediction or the inter prediction may be used,and in case of using the inter prediction, maximally up to bi-predictionmay be used.

In accordance with the characteristics (e.g., resolution) of the videoimage, or in consideration of the coding efficiency or parallelprocessing, the encoder may determine the tile/tile group, brick, slice,maximum and minimum coding unit sizes, and corresponding information orinformation capable of inducing the same may be included in thebitstream.

The decoder may obtain information representing whether the tile/tilegroup, brick, slice, or CTU in the tile of the current picture has beenpartitioned into a plurality of coding units. By obtaining(transmitting) such information only under a specific condition, theefficiency can be enhanced.

Meanwhile, as described above, one picture may include a plurality ofslices, and one slice may include a slice header and slice data. In thiscase, one picture header may be further added for the plurality ofslices (set of the slice header and slice data) in one picture. Thepicture header (picture header syntax) may includeinformation/parameters capable of being commonly applied to the picture.The slice header (slice header syntax) may includeinformation/parameters capable of being commonly applied to the slice.An adaptation parameter set (APS) or a picture parameter set (PPS) mayinclude information/parameters capable of being commonly applied to oneor more pictures. A sequence parameter set (SPS) may includeinformation/parameters capable of being commonly applied to one or moresequences. A video parameter set (VPS) may includeinformation/parameters capable of being commonly applied to multiplelayers. A decoding parameter set (DPS) may includeinformation/parameters capable of being commonly applied to the overallvideo. The DPS may include information/parameters related toconcatenation of a coded video sequence (CVS).

In the present document, an upper layer syntax may include at least oneof the APS syntax, PPS syntax, SPS syntax, VPS syntax, DPS syntax,picture header syntax, and slice header syntax.

Further, for example, information on the division and the configurationof the tile/tile group/brick/slice may be configured by the encoding endthrough the upper level syntax, and may be transferred to the decodingapparatus in the form of a bitstream.

In the present document, at least one of quantization/dequantizationand/or transform/inverse transform may be omitted. When thequantization/dequantization is omitted, the quantized transformcoefficient may be referred to as a transform coefficient. When thetransform/inverse transform is omitted, the transform coefficient may becalled a coefficient or a residual coefficient or may still be calledthe transform coefficient for uniformity of expression.

In the present document, the quantized transform coefficient and thetransform coefficient may be referred to as a transform coefficient anda scaled transform coefficient, respectively. In this case, the residualinformation may include information on transform coefficient(s), and theinformation on the transform coefficient(s) may be signaled throughresidual coding syntax. Transform coefficients may be derived based onthe residual information (or information on the transformcoefficient(s)), and scaled transform coefficients may be derivedthrough inverse transform (scaling) on the transform coefficients.Residual samples may be derived based on inverse transform (transform)of the scaled transform coefficients. This may be applied/expressed inother parts of the present document as well.

As the above-described contents, the encoding apparatus may performvarious encoding methods, for example, such as exponential Golomb,context-adaptive variable length coding (CAVLC), and context-adaptivebinary arithmetic coding (CABAC). Further, the decoding apparatus maydecode information in the bitstream based on the coding method, such asthe exponential Golomb, CAVLC, or CABAC, and may output a value of asyntax element and quantized values of transform coefficients forresidual, being necessary for image reconstruction. For example, theabove-described coding methods may be performed as in the contents to bedescribed later.

In the present document, the intra prediction may represent theprediction that generates the prediction samples for the current blockbased on the reference samples in the picture (hereinafter, currentpicture) to which the current block belongs. In case that the intraprediction is applied to the current block, the neighboring referencesamples to be used for the intra prediction of the current block may bederived. The neighboring reference samples of the current block mayinclude a sample adjacent to the left boundary of the current blockhaving the size of nW×nH and total 2×nH samples neighboring thebottom-left, a sample adjacent to the top boundary of the current blockand total 2×nW samples neighboring the top-right, and one sampleneighboring the top-left of the current block. Further, the neighboringreference samples of the current block may include a plurality ofcolumns of top neighboring samples and a plurality of rows of leftneighboring samples. Further, the neighboring reference samples of thecurrent block may include total nH samples adjacent to the rightboundary of the current block having the size of nW×nH, total nW samplesadjacent to the bottom boundary of the current block, and one sampleneighboring the bottom-right of the current block.

However, some of the neighboring reference samples of the current blockmay have not yet been decoded or enabled. In this case, the decodingapparatus may configure the neighboring reference samples to be used forthe prediction through substation of enabled samples for non-enabledsample. Further, the neighboring reference samples to be used for theprediction may be configured through interpolation of the enabledsamples.

In case that the neighboring reference samples are derived, (i) theprediction sample may be induced based on an average or interpolation ofthe neighboring reference samples of the current block, and (ii) theprediction sample may be induced based on the reference sample that ispresent in a specific (prediction) direction for the prediction sampleamong the neighboring reference samples of the current block. The caseof (i) may be called a non-directional mode or a non-angular mode, andthe case of (ii) may be called a directional mode or an angular mode.Further, the prediction sample may be generated through interpolation ofthe first neighboring sample with the second neighboring sample locatedin an opposite direction to the prediction direction of the intraprediction mode of the current block based on the prediction sample ofthe current block among the neighboring reference samples. Theabove-described case may be called a linear interpolation intraprediction (LIP). Further, chroma prediction samples may be generatedbased on luma samples by using a linear model. This case may be calledan LM mode. Further, a temporary prediction sample of the current blockmay be derived based on the filtered neighboring reference samples, anda prediction sample of the current block may be derived by calculating aweighted sum of the temporary prediction sample and at least onereference sample derived in accordance with the intra prediction modeamong the existing neighboring reference samples, that is, non-filteredneighboring reference samples. The above-described case may be called aposition dependent intra prediction (PDPC). Further, the predictionsample may be derived by using a reference sample located in aprediction direction on a reference sample line having the highestprediction accuracy among neighboring multiple reference sample lines ofthe current block through selection of the corresponding line, and inthis case, intra prediction coding may be performed in a method forindicating (signaling) the used reference sample line to the decodingapparatus. The above-described case may be called multi-reference line(MRL) intra prediction or MRL-based intra prediction. Further, the intraprediction may be performed based on the same intra prediction modethrough division of the current block into vertical or horizontalsubpartitions, and the neighboring reference samples may be derived andused in the unit of a subpartition. That is, in this case, since theintra prediction mode for the current block is equally applied to thesubpartitions, and the neighboring reference samples are derived andused in the unit of the subpartition, the intra prediction performancecan be enhanced in some cases. Such a prediction method may be calledintra subpartitions (ISP) or ISP-based intra prediction. Theabove-described intra prediction method may be called the intraprediction type in distinction from the intra prediction mode. The intraprediction type may be called by various terms, such as an intraprediction technique or an additional intra prediction mode. Forexample, the intra prediction type (or additional intra prediction mode)may include at least one of LIP, PDPC, MRL, or ISP described above. Ageneral intra prediction method excluding a specific intra predictiontype, such as the LIP, PDPC, MRL, or ISP, may be called a normal intraprediction type. The normal intra prediction type may be generallyapplied in case that the specific intra prediction type is not applied,and the prediction may be performed based on the above-described intraprediction mode. Meanwhile, as needed, post-filtering for the derivedprediction sample may be performed.

Specifically, the intra prediction procedure may include steps of intraprediction mode/type determination, neighboring reference samplederivation, and intra prediction mode/type-based prediction samplederivation. Further, as needed, a post-filtering step for the derivedprediction sample may be performed.

Meanwhile, in addition to the above-described prediction types, anaffine linear weighted intra prediction (ALWIP) may be used. The ALWIPmay be called linear weighted intra prediction (LWIP) or matrix weightedintra prediction (MIP) or matrix based intra prediction. In case thatthe MIP is applied for the current block, i) by using the neighboringreference samples for which an averaging procedure has been performedii) a matrix-vector-multiplication procedure may be performed, and iii)as needed, the prediction samples for the current block may be derivedby further performing a horizontal/vertical interpolation. The intraprediction modes being used for the MIP may be configured differentlyfrom the above-described LIP, PDPC, MRL, or ISP intra prediction, or theintra prediction modes being used for the normal intra prediction. Theintra prediction mode for the MIP may be called an MIP intra predictionmode, an MIP prediction mode, or an MIP mode. For example, in accordancewith the intra prediction mode for the MIP, a matrix and an offset beingused for the matrix vector multiplication may be differently configured.Here, the matrix may be called an (MIP) weighted matrix, and the offsetmay be called an (MIP) offset vector or an (MIP) bias vector.

FIG. 4 represents an example of an entropy encoding method, and FIG. 5represents an example of an entropy decoding method.

In an example, FIG. 4 shows an encoding process of CABAC for encodingone syntax element, and FIG. 5 shows a decoding process of CABAC fordecoding one syntax element.

In a case where an input signal is a syntax element which is not abinary value, the encoding process of CABAC first converts the inputsignal into a binary value through binarization. In a case where aninput signal is already a binary value, the input signal bypasses thebinarization without being subject to it. Here, each binary number 0 or1 constituting a binary value is referred to as a bin. For example, in acase where a binary string (bin string) after the binarization is ‘110’,each of 1, 1, and 0 is referred to as a bin. The bin(s) for a syntaxelement may represent a value of the syntax element.

Binarized bins are input to a regular coding engine or a bypass codingengine. The regular coding engine assigns to a corresponding bin acontext model reflecting a probability value, and encodes thecorresponding bin based on the assigned context model. After performingthe coding on each bin, the regular coding engine may update aprobability model for the bin. The thus coded bins are referred to ascontext-coded bins. The bypass coding engine omits a process ofestimating a probability for an input bin, and a process of updating theprobability model which has been applied to the bin, after the coding.The bypass coding engine improves a coding speed by coding bins beinginput thereto while applying uniform probability distribution (e.g.,50:50) to them instead of assigning a context. The thus coded bins arereferred to as bypass bins. The context model may be allocated andupdated for each bin to be context coded (regular coded), and thecontext model may be indicated based on ctxidx or ctxInc. ctxidx may bederived based on ctxInc. Specifically, for example, the context index(ctxidx) indicating the context model for each of the regularly codedbins may be derived as the sum of the context index increment (ctxInc)and the context index offset (ctxIdxOffset). Here, the ctxInc may bederived differently for each bin. The ctxIdxOffset may be represented asthe lowest value of the ctxIdx. The minimum value of the ctxIdx may bereferred to as an initial value (initValue) of the ctxIdx. ThectxIdxOffset is a value generally used for distinction from contextmodels for other syntax elements, and a context model for one syntaxelement may be distinguished/derived based on ctxinc.

In the entropy encoding process, it may be determined whether to performthe encoding through the regular coding engine or through the bypasscoding engine, and a coding path may be switched. The entropy decodingperforms the same processes as those of the entropy encoding in areverse order.

The above-described entropy coding, for example, may be performed asfollows.

Referring to FIG. 4 , the encoding apparatus (entropy encoder) performsan entropy coding process on image/video information. The image/videoinformation may include partitioning-related information,prediction-related information (e.g., inter/intra predictiondistinguishing information, intra prediction mode information, interprediction mode information, or the like), residual information, in-loopfiltering-related information, or may include various syntax elementsrelated to them. The entropy coding may be performed in units of syntaxelements.

Specifically, the encoding apparatus performs binarization on a targetsyntax element (S400). Here, the binarization may be based on variousbinarization methods such as Truncated Rice binarization process,Fixed-length binarization process, and the like, and the binarizationmethod for the target syntax element may be predefined. The binarizationprocedure may be performed by a binarizer 242 in the entropy encoder240.

And the encoding apparatus performs entropy encoding on the targetsyntax element (S410). The encoding apparatus may regular coding-based(context-based) or bypass coding-based encode a bin string of the targetsyntax element based on a entropy coding scheme such as context-adaptivearithmetic coding (CABAC) or context-adaptive variable length coding(CAVLC), and the output thereof may be incorporated into the bitstream.The entropy encoding process may be performed by an entropy encodingprocessor 243 in the entropy encoder 240. As described above, thebitstream may be transferred to the decoding apparatus through a(digital) storage medium or a network.

The decoding apparatus (entropy decoder) may decode encoded image/videoinformation. The image/video information may includepartitioning-related information, prediction-related information (e.g.,inter/intra prediction distinguishing information, intra prediction modeinformation, inter prediction mode information, or the like), residualinformation, in-loop filtering-related information, or may includevarious syntax elements related to them. The entropy coding may beperformed in units of syntax elements.

Referring to FIG. 5 , the decoding apparatus performs binarization on atarget syntax element (S510). Here, the binarization may be based onvarious binarization methods such as Truncated Rice binarizationprocess, Fixed-length binarization process, and the like, and thebinarization method for the target syntax element may be predefined. Thedecoding apparatus may derive available bin strings (bin stringcandidates) for available values of the target syntax element throughthe binarization process. The binarization procedure may be performed bya binarizer 312 in the entropy decoder 310.

Then, the decoding apparatus performs entropy decoding on the targetsyntax element (S520). While decoding and parsing sequentiallyrespective bins for the target syntax element from the input bit(s) inthe bitstream, the decoding apparatus compares the derived bin stringwith enabled bin strings for the corresponding syntax element. When thederived bin string is the same as one of the enabled bin strings, thevalue corresponding to the bin string is derived as a value of thesyntax element. If otherwise, the decoding apparatus performs theabove-described process again after further parsing a next bit in thebitstream. Through these processes, even without using a start bit or anend bit for specific information (specific syntax element) in abitstream, the decoding apparatus may signal the information using avariable length bit. Through this, relatively less bits may be assignedto a low value, thereby increasing an overall coding efficiency.

The decoding apparatus may perform context-based or bypass-baseddecoding on respective bins in the bin string from a bitstream based onan entropy coding technique such as CABAC, CAVLC or the like. Theentropy decoding process may be performed by an entropy decodingprocessor 313 in the entropy decoder 310. The bitstream may includevarious information for image/video decoding as described above. Asdescribed above, the bitstream may be transferred to the decodingapparatus through a (digital) storage medium or a network.

In this document, a table (syntax table) including syntax elements maybe used to indicate signaling of information from the encoding apparatusto the decoding apparatus. An order of syntax elements in a tableincluding the syntax elements used in this document may indicate aparsing order of syntax elements from a bitstream. The encodingapparatus may construct and encode the syntax table so that the syntaxelements can be parsed by the decoding apparatus in a parsing order,while the decoding apparatus may obtain values of the syntax elements byparsing and decoding the syntax elements of the corresponding syntaxtable from the bitstream according to the parsing order.

FIG. 6 represents an example of a picture decoding process.

FIG. 6 shows an example of a schematic picture decoding process to whichembodiment(s) of this document can be applied. In FIG. 6 , S600 may beperformed in the entropy decoder 310 of the decoding apparatus describedabove in FIG. 3 ; S610 may be performed in the predictor 330; S620 maybe performed in the residual processor 320; S630 may be performed in theadder 340; and S640 may be performed in the filter 350. S600 may includethe information decoding process described in the present document; S610may include the inter/intra prediction process described in the presentdocument; S620 may include the residual processing process described inthe present document; S630 may include the block/picture reconstructionprocess described in the present document; and S640 may include thein-loop filtering process described in the present document.

Referring to FIG. 6 , as represented in the description with regard toFIG. 3 , the picture decoding process may schematically include animage/video information obtaining process S600 from a bitstream (throughdecoding), a picture reconstruction process S610 to S630, and an in-loopfiltering process S640 for the reconstructed picture. The picturereconstruction process may be performed based on the residual samplesand the prediction samples obtained through the inter/intra predictionS610 and the residual processing S620 (dequantization for the quantizedtransform coefficient, inverse transform) process described in thepresent document. Through the in-loop filtering process for thereconstructed picture which has been generated though the picturereconstruction process, a modified reconstructed picture may begenerated, which may be output as a decoded picture, and may also bestored in the decoding picture buffer or a memory 360 of the decodingapparatus and be used as a reference picture in the inter predictionprocess of the later picture decoding. According to circumstances, thein-loop filtering process may be skipped, and in this case, thereconstructed picture may be output as a decoded picture, and may alsobe stored in the decoding picture buffer or a memory 360 of the decodingapparatus and be used as a reference picture in the inter predictionprocess of the later picture decoding. The in-loop filtering processS640 may include the deblocking filtering process, the sample adaptiveoffset (SAO) process, the adaptive loop filter (ALF) process, and/or thebi-lateral filter process as described above, and all or some of themmay be skipped. Further, one or some of the deblocking filteringprocess, the sample adaptive offset (SAO) process, the adaptive loopfilter (ALF) process, and the bi-lateral filter processes may besequentially applied, or all of them may be sequentially applied. Forexample, after the deblocking filtering process is applied to thereconstructed picture, the SAO process may be performed thereon.Alternatively, for example, after the deblocking filtering process isapplied to the reconstructed picture, the ALF process may be performedthereon. This may be likewise performed in the encoding apparatus.

FIG. 7 represents an example of a picture encoding process.

FIG. 7 shows an example of a schematic picture encoding process to whichembodiment(s) of this document can be applied. In FIG. 7 , S700 may beperformed in the predictor 220 of the encoding apparatus described abovein FIG. 2 ; S710 may be performed in the residual processor 230; andS720 may be performed in the entropy encoder 240. S700 may include theinter/intra prediction process described in the present document; S710may include the residual processing process described in the presentdocument; and S720 may include the information encoding processdescribed in the present document.

Referring to FIG. 7 , the picture encoding process may schematicallyinclude, as represented in the description with regard to FIG. 2 , aprocess of generating a reconstructed picture for a current picture anda process (optional) of applying in-loop filtering to the reconstructedpicture, as well as a process of encoding information for picturereconstruction (e.g., prediction information, residual information,partitioning information or the like) and outputting it in the form of abitstream. The encoding apparatus may derive (modified) residual samplesfrom a quantized transform coefficient through the dequantizer 234 andthe inverse transformer 235, and may generate a reconstructed picturebased on the (modified) residual samples and the prediction samples,which are the outputs of S700. The reconstructed picture generated inthis way may be the same as the above-described reconstructed picturegenerated in the decoding apparatus. Through the in-loop filteringprocess for the reconstructed picture, the modified reconstructedpicture may be generated, which may be stored in the decoding picturebuffer or a memory 270, and used as a reference picture in the interprediction process of the later picture encoding, similarly to the caseof the decoding apparatus. As described above, all or a part of thein-loop filtering process may be skipped according to circumstances. Ina case where the in-loop filtering process is performed, (in-loop)filtering-related information (parameter) may be encoded in the entropyencoder 240 and output in the form of a bitstream, and the decodingapparatus may perform the in-loop filtering process in the same way asthat of the encoding apparatus based on the filtering-relatedinformation.

Through this in-loop filtering process, it is possible to reduce noises,such as blocking artifact and ringing artifact, which are generatedduring the image/video coding, and to increase subjective/objectivevisual quality. Further, as the in-loop filtering process is performedin both the encoding apparatus and the decoding apparatus, the encodingapparatus and the decoding apparatus can derive the same predictionresult, increase the reliability of the picture coding, and reduce theamount of data to be transmitted for picture coding.

As described above, the picture reconstruction procedure may beperformed in the encoding apparatus as well as in the decodingapparatus. Based on intra prediction/inter prediction on each blockunit, a reconstructed block may be generated, and a reconstructedpicture including the reconstructed blocks may be generated. In a casewhere a current picture/slice/tile group is an I picture/slice/tilegroup, the blocks included in the current picture/slice/tile group maybe reconstructed only based on the intra prediction. Meanwhile, in acase where a current picture/slice/tile group is a P or Bpicture/slice/tile group, the blocks included in the currentpicture/slice/tile group may be reconstructed based on the intraprediction or inter prediction. In this case, the inter prediction maybe applied to some of the blocks in the current picture/slice/tilegroup, and the intra prediction may be applied to some of the rest ofthe blocks. A colour component of the picture may include a lumacomponent and a chroma component, and the methods and embodimentsproposed in this document may be applied to the luma component and thechroma component unless explicitly limited in this document.

Meanwhile, the video/image encoding process based on inter predictionmay schematically include, for example, the following.

FIG. 8 represents an example of an inter prediction based video/imagedecoding method.

Referring to FIG. 8 , the encoding apparatus performs inter predictionon the current block (S800). The encoding apparatus may derive interprediction mode and motion information of the current block, andgenerate prediction samples of the current block. Here, inter predictionmode determination, motion information derivation, and prediction samplegeneration process may be performed at the same time, or performed oneafter another. For example, the inter predictor of the encodingapparatus may include a prediction mode determiner, a motion informationderiver, and a predicted sample deriver. The prediction mode determinermay determine a prediction mode for the current block, the motioninformation deriver may derive motion information of the current block,and the prediction sample deriver may derive predicted samples of thecurrent block. For example, the inter predictor of the encodingapparatus may search for a block similar to the current block in acertain region (search region) of the reference pictures through motionestimation, and derive a reference block whose difference from thecurrent block is minimum, or less than or equal to a certain level.Based on this, the reference picture index indicating a referencepicture on which the reference block is located may be derived, and themotion vector may be derived based on the difference in position betweenthe reference block and the current block. The encoding apparatus maydetermine a mode from among various prediction modes, which is appliedto the current block. The encoding apparatus may compare rate-distortion(RD) costs for the various prediction modes, and determine the optimalprediction mode for the current block.

For example, when the skip mode or the merge mode is applied to thecurrent block, the encoding apparatus may construct a merge candidatelist, and derive a reference block whose difference from the currentblock is minimum or less than or equal to a certain level from amongreference blocks which merge candidates included in the merge candidatelist indicate. In this case, the merge candidate associated with thederived reference block may be selected, and merge index informationindicating the selected merge candidate may be generated and be signaledto the decoding apparatus. The motion information of the current blockmay be derived using motion information of the selected merge candidate.

As another example, when the (A)MVP mode is applied to the currentblock, the encoding apparatus may construct an (A)MVP candidate list,and use the motion vector of an mvp (motion vector predictor) candidateselected from among mvp candidates included in the (A)MVP candidate listas the mvp of the current block. In this case, for example, the motionvector indicating the reference block derived by the above-describedmotion estimation may be used as a motion vector of the current block,and among the mvp candidates, the mvp candidate which has a motionvector whose difference from the motion vector of the current block issmallest may be the selected mvp candidate. MVD (motion vectordifference), which is a difference obtained by subtracting the mvp fromthe motion vector of the current block, may be derived. In this case,the information on the MVD may be signaled to the decoding apparatus.Additionally, when the (A)MVP mode is applied, a value of the referencepicture index may be configured as a reference picture index informationand signaled separately to the decoding apparatus.

The encoding apparatus may derive residual samples based on theprediction samples (S810). The encoding apparatus may derive theresidual samples via comparison of original samples of the current blockand the prediction samples.

The encoding apparatus encodes image information including predictioninformation and residual information (S820). The encoding apparatus mayoutput the encoded image information in the form of a bitstream. Theprediction information may include a prediction mode information (e.g.,skip flag, merge flag, mode index or the like) and information on motioninformation as information on the prediction procedure. The informationon motion information may include candidate selection information (e.g.,merge index, mvp flag, or mvp index), which is information for derivinga motion vector. Further, the information on motion information mayinclude information on the above-described MVD, and/or the referencepicture index information. Further, the information on motioninformation may include information indicating whether the L0prediction, the L1 prediction, or bi-prediction is applied. The residualinformation is information on the residual samples. The residualinformation may include information on quantized transform coefficientsfor the residual samples.

The output bitstream may be stored in a (digital) storage medium andtransferred to the decoding apparatus, or may be transferred to thedecoding apparatus through a network.

Meanwhile, as described above, the encoding apparatus may generate areconstructed picture (including reconstructed samples and areconstructed block) based on the reference samples and the residualsamples. This is to derive the same prediction result in the encodingapparatus as one that is performed in the decoding apparatus, and thereason is that coding efficiency can be increased through this.Therefore, the encoding apparatus may store a reconstructed picture (orreconstructed samples, a reconstructed block) in the memory, and utilizeit as a reference picture for inter prediction. The in-loop filteringprocess and the like may be further applied to the reconstructed pictureas described above.

The video/image decoding procedure based on inter prediction mayschematically include, for example, the following.

FIG. 9 represents an example of an inter prediction based video/imagedecoding method.

The decoding apparatus may perform an operation corresponding to theoperation which has been performed in the encoding apparatus. Thedecoding apparatus may perform prediction on the current block andderive the prediction samples based on the received predictioninformation.

Specifically, referring to FIG. 9 , the decoding apparatus may determinethe prediction mode for the current block based on the receivedprediction information from the bitstream (S900). The decoding apparatusmay determine which inter prediction mode is applied to the currentblock based on the prediction mode information in the predictioninformation.

For example, it may be determined whether the merge mode is applied tothe current block or (A)MVP mode is determined based on the merge flag.Alternatively, one inter prediction mode may be selected from amongvarious inter prediction mode candidates based on the merge index. Theinter prediction mode candidates may include various inter predictionmodes, such as skip mode, merge mode, and/or (A)MVP mode.

The decoding apparatus derives the motion information of the currentblock based on the determined inter prediction mode (S910). For example,when the skip mode or the merge mode is applied to the current block,the decoding apparatus may construct a merge candidate list to bedescribed later, and select one of merge candidates included in themerge candidate list. The selection may be performed based on theabove-described selection information (merge index). The motioninformation of the current block may be derived using motion informationof the selected merge candidate. The motion information of the selectedmerge candidate may be used as the motion information of the currentblock.

In another example, when the (A)MVP mode is applied to the currentblock, the decoding apparatus may construct an (A)MVP candidate list,and use the motion vector of an mvp (motion vector predictor) candidateselected from among mvp candidates included in the (A)MVP candidate listas the mvp of the current block. The selection may be performed based onthe above-described selection information (mvp flag or mvp index). Inthis case, MVD of the current block may be derived based on informationon the MVD, and the motion vector of the current block may be derivedbased on the MVD and the MVP of the current block. Further, thereference picture index of the current block may be derived based on thereference picture index information. The picture in the referencepicture list concerning the current block, which the reference pictureindex indicates may be derived as a reference picture which is referredto for the inter prediction of the current block.

Meanwhile, motion information of the current block may be derivedwithout constructing a candidate list, and in this case, theconstructing of the candidate list as described above may be omitted.

The decoding apparatus may generate prediction samples for the currentblock based on the motion information of the current block (S920). Inthis case, the reference picture may be derived based on the referencepicture index of the current block, and the prediction samples of thecurrent block may be derived using the samples of the reference block onthe reference picture, which is indicated by the motion vector of thecurrent block. In this case, a prediction sample filtering process forthe all or some of prediction samples of the current block may befurther performed according to circumstances as described later.

For example, the inter predictor of the encoding apparatus may include aprediction mode determiner, a motion information deriver, and apredicted sample deriver, may determine a prediction mode for thecurrent block based on prediction mode information received at theprediction mode determiner, may derive motion information (motion vectorand/or reference picture index and/or the like) of the current blockbased on information on motion information received at the motioninformation deriver, and may derive predicted samples of the currentblock at the prediction sample deriver.

The decoding apparatus generates the residual samples for the currentblock based on the received residual information (S930). The decodingapparatus may generate the reconstructed samples for the current blockbased on the residual samples and the prediction samples, and generatethe reconstructed picture based on these reconstructed samples (S940).Hereinafter, the in-loop filtering procedure or the like may be appliedto the reconstructed picture as described above.

Meanwhile, as described above, a high level syntax (HLS) may becoded/signaled for video/image coding. The coded picture may be composedof one or more slices. A parameter describing the coded picture issignaled in the picture header, and a parameter describing the slice issignaled in the slice header. The picture header is carried in the formof a NAL unit itself. The slice header is present at a start portion ofthe NAL unit including a payload of the slice (i.e., slice data).

Each picture is related to a picture header. The picture may be composedof different types of slices (intra-coded slice (i.e., I slice) andinter-coded slice (i.e., P slice and B slice)). Accordingly, the pictureheader may include syntax elements necessary for the intra slice of thepicture and the inter slice of the picture. For example, the syntax ofthe picture header may be as in the following Table 1.

TABLE 1 Descriptor picture_header_rbsp( ) {  non_reference_picture_flag u (1)  gdr_pic_flag  u (1)  no_output_of_prior_pics_flag  u (1)  if(gdr_pic_flag )   recovery_poc_cnt ue (e)  ph_pic_parameter_set_id ue (v) if( sps_poc_msb_flag ) {   ph_poc_msb_present_flag  u (1)   if(ph_poc_msb_present_flag )    poc_msb_val  u (v)  }  if(sps_subpic_id_present_flag && !sps_subpic_id_signalling_flag ) {  ph_subpic_id_signalling_present_flag  u (1)   if(ph_subpic_id_signalling_present_flag ) {    ph_subpic_id_len_minus1 ue(v)    for( i = 0;i <= sps_num_subpics_minus1; i++ )     ph_subpic_id[ i]  u (v)   }  }  if(!sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) {  ph_loop_filter_across_virtual_boundaries_disabled_present_flag  u (1)  if( ph_loop_filter_across_virtual_boundaries_disabled_present_flag ) {   ph_num_ver_virtual_boundaries  u (2)    for( i = 0; i <ph_num_ver_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_x[ i] u (13)    ph_num_hor_virtual_boundaries  u (2)    for( i = 0; i <ph_num_hor_virtual_boundaries; i++ )     ph_virtual_boundaries_pos_y[ i] u (13)   }  }  if( seperate_colour_plane_flag = = 1 )  colour_plane_id  u (2)  if( output_flag_present_flag )  pic_output_flag  u (1)  pic_rpl_present_flag  u (1)  if(pic_rpl_present_flag ) {   for( i = 0; i < 2; i++ ) {    if(num_ref_pic_lists_in_sps[ i ] > 0 && !pps_ref_pic_lists_sps_idc[ i ] &&      ( i = = 0 | | ( i = = 1 && rpl1_idx_present_flag ) ) )    pic_rpl_sps_flag[ i ]  u (1)    if( pic_rpl_sps_flag[ i ] ) {    if( num_ref_pic_lists_in_sps[ i ] > 1 &&        ( i = = 0 | | ( i == 1 && rpl1_idx_present_flag ) ) )      pic_rpl_idx[ i ]  u (v)    }else     ref_pic_list_struct(i, num_ref_pic_lists_in_sps[ i ] )    for(j = 0; j < NumLtrpEntries[ i ][ RplsIdx[ i ] ]; j++ ) {     if(ltrp_in_slice_header_flag[ i ][ RplsIdx[ i ] ] )      pic_poc_lsb_lt[ i][ j ]  u (v)     pic_delta_poc_msb_present_flag[ i ][ j ]  u (1)    if( pic_delta_poc_msb_present_flag[ i ][ j ] )     pic_delta_poc_msb_cycle_lt[ i ][ j ] ue (v)    }   }  }  if(partitions_constraints_override_enabled_flag ) {  partitions_constraints_override_flag ue (v)   if(partitions_constraints_override_flag ) {    

 

ue (v)    pic_log2_diff_min_qt_min_cb_inter_slice ue (v)   pic_max_mtt_hierarchy_depth_inter_slice ue (v)    

 

   if( pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {     

 

ue (v)     

 

ue (v)    }    if( pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {    pic_log2_diff_max_bt_min_qt_inter_slice ue (v)    pic_log2_diff_max_tt_min_qt_inter_slice ue (v)    }    if(qtbtt_dual_tree_intra_flag ) {     

 

ue (v)     

 

ue (v)     if( pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {     

 

ue (v)      

 

ue (v)     }    }   }  }  if( cu_qp_delta_enabled_flag )   

 

ue (v)   pic_cu_qp_delta_subdiv_inter_slice ue (v)  }  if(pps_cu_chroma_qp_offset_list_enabled_flag ) {   

 

ue (v)   pic_cu_chroma_qp_offset_subdiv_inter_slice  }  if(sps_temporal_mvp_enabled_flag )   pic_temporal_mvp_enabled_flag  u (1) if(!pps_mvd_l1_zero_idc )   mvd_l1_zero_flag  u (1)  if(!pps_six_minus_max_num_merge_cand_plus1 )  pic_six_minus_max_num_merge_cand ue (v)  if( sps_affine_enabled_flag )  pic_five_minus_max_num_subblock_merge_cand ue (v)  if(sps_fpel_mmvd_enabled_flag )   pic_fpel_mmvd_enabled_flag  u (1)  if(sps_bdof_pic_present_flag )   pic_disable_bdof_flag  u (1)  if(sps_dmvr_pic_present_flag )   pic_disable_dmvr_flag  u (1)  if(sps_prof_pic_present_flag )   pic_disable_prof_flag  u (1)  if(sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&   !pps_max_num_merge_cand_minus_max_num_triangle_cand_plus1 )  pic_max_num_merge_cand_minus_max_num_triangle_cand ue (v)  if(sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue (v) if( sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag  u (1) if( sps_sao_enabled_flag ) {    pic_sao_enabled_present_flag  u (1)  if( pic_sao_enabled_present_flag ) {    pic_sao_luma_enabled_flag  u(1)    if( ChromaArrayType != 0 )     pic_sao_chroma_enabled_flag  u (1)  }  }  if( sps_alf_enabled_flag ) {   pic_alf_enabled_present_flag  u(1)   if( pic_alf_enabled_present_flag ) {    pic_alf_enabled_flag  u(1)    if( pic_alf_enabled_flag ) {     pic_num_alf_aps_ids_luma  u (3)    for( i = 0; i < pic_num_alf_aps_ids_luma; i++ )     pic_alf_aps_id_luma[ i ]  u (3)     if( ChromaArrayType != 0 )     pic_alf_chroma_idc  u (2)     if( pic_alf_chroma_idc )     pic_alf_aps_id_chroma  u (3)    }   }  }  if(!pps_dep_quant_enabled_flag )   pic_dep_quant_enabled_flag  u (1)  if(!pic_dep_quant_enabled_flag )   sign_data_hiding_enabled_flag  u (1) if( deblocking_filter_override_enabled_flag ) {  pic_deblocking_filter_override_enabled_flag  u (1)   if(pic_deblocking_filter_override_enabled_flag ) {   pic_deblocking_filter_override_flag  u (1)    if(pic_deblocking_filter_override_flag ) {    pic_deblocking_filter_disabled_flag  u (1)     if(!pic_deblocking_filter_disabled_flag ) {      pic_beta_offset_div2 se(v)      pic_tc_offset_div2 se (v)     }    }   }  }  if(sps_lmcs_enabled_flag ) {   pic_lmcs_enabled_flag  u (1)   if(pic_lmcs_enabled_flag ) {    pic_lmcs_aps_id  u (2)    if(ChromaArrayType != 0 )     pic_chroma_residual_scale_flag  u (1)   }  } if( sps_scaling_list_enabled_flag ) {   pic_scaling_list_enabled_flag u (1)   if( pic_scaling_list_enabled_flag )    pic_scaling_list_aps_id u (3)  }  if( picture_header_extension_present_flag ) {  ph_extension_length ue (v)   for( i = 0; i < ph_extension_length; i++)   ph_extension_data_byte[ i ]  u (8)  }  rbsp_trailing_bits( ) }

Among syntax elements of Table 1, syntax elements including“intra_slice” in their titles (e.g., pic_log2_diff_min_qt_min_cb_intra_slice_luma) are syntax elements being used inI slice of the corresponding picture, and syntax elements (e.g.,pic_temporal_mvp_enabled_flag) related to syntax elements including“inter_slice” in their titles (e.g., pic_log2_diff_min_qt_min_cb_inter_slice, mvp, mvd, mmvd, and merge) are syntaxelements being used in P slice and/or B slice of the correspondingpicture.

That is, the picture header includes all of syntax elements necessaryfor the intra-coded slice and syntax elements necessary for theinter-coded slice for every single picture. However, this is useful onlywith respect to the picture including mixed type slices (pictureincluding all of the intra-coded slice and the inter-coded slice). Ingeneral, since the picture does not include the mixed type slices (i.e.,the general picture includes only the intra-coded slices or only theinter-coded slices), it is unnecessary to perform signaling of all data(syntax elements being used in the intra-coded slice and syntax elementsbeing used in the inter-coded slice).

The following drawings have been prepared to explain a detailed exampleof the present document. Since the name of a detailed device or the nameof detailed signal/information is exemplarily presented, the technicalfeatures of the present document are not limited to the detailed namesused in the following drawing.

The present document provides the following methods in order to solvethe above-described problem. Items of each method may be individuallyapplied, or may be applied in combination.

1. A flag in picture header to specify whether syntax elements that areneeded only by intra coded slices are present in the picture header maybe signaled. The flag may be referred to asintra_signaling_present_flag.

a) When intra_signaling_present_flag is equal to 1, syntax elements thatare needed by intra coded slices are present in the picture header.Likewise, when intra_signaling_present_flag is equal to 0, syntaxelements that are needed by intra coded slices are not present in thepicture header.

b) The value of intra_signaling_present_flag in a picture header shallbe equal to 1 on the picture associated with the picture header has atleast one intra coded slice.

c) The value of intra_signaling_present_flag in a picture header may beequal to 1 even when the picture associated with the picture header doesnot have intra coded slice.

d) When a picture has one or more subpicture(s) containing intra codedslices only and it is anticipated that one or more of the subpicture(s)may be extracted and merged with subpictures which contains one or moreinter coded slices, the value of intra_signaling_present_flag should beset equal to 1.

2. A flag in picture header to specify whether syntax elements that areneeded only by inter coded slices are present in the picture header maybe signaled. The flag may be referred to asinter_signaling_present_flag.

a) When inter_signaling_present_flag is equal to 1, syntax elements thatare needed by inter coded slices are present in the picture header.Likewise, when inter_signaling_present_flag is equal to 0, syntaxelements that are needed by inter coded slices are not present in thepicture header.

b) The value of inter_signaling_present_flag in a picture header shallbe equal to 1 on the picture associated with the picture header has atleast one inter coded slice.

c) The value of inter_signaling_present_flag in a picture header may beequal to 1 even when the picture associated with the picture header doesnot have inter coded slice.

d) When a picture has one or more subpicture(s) containing inter codedslices only and it is anticipated that one or more of the subpicture(s)may be extracted and merged with subpictures which contains one or moreintra coded slices, the value of inter_signaling_present_flag should beset equal to 1.

3. The above flags (intra_signaling_present_flag andinter_signaling_present_flag) may be signaled in other parameter setsuch as picture parameter set (PPS) instead of in picture header).

4. Another alternative for signaling the above flags can be as follow.

a) Two variables IntraSignalingPresentFlag and InterSignalingPresentFlagwhich specify whether syntax elements needed by intra coded slices andsyntax element needed by inter coded slices, respectively, present inthe picture header or not may be defined.

b) A flag called mixed_slice_types_present_flag in the picture headermay be signaled. When mixed_slice_types_present_flag is equal to 1, thevalue of IntraSignalingPresentFlag and InterSignalingPresentFlag are setto be equal to 1.

c) When mixed_slice_types_present_flag is equal to 0, additional flagcalled intra_slice_only_flag may be signaled in the picture header andthe following applies. If intra_slice_only_flag is equal to 1, the valueof IntraSignalingPresentFlag is set equal to 1 and the value ofInterSignalingPresentFlag is set equal to 0. Otherwise, the value ofIntraSignalingPresentFlag is set equal to 0 and the value ofInterSignalingPresentFlag is set equal to 1.

5. A fixed length syntax element in picture header, which may be calledslice_types_idc, which specifies the following information may besignaled.

a) Whether the picture associated with the picture header contain intracoded slices only. For this type, the value of slice_types_idc may beset equal to 0.

b) Whether the picture associated with the picture header contain intercoded slices only. The value of slice_types_idc may be set equal to 1.

c) Whether the picture associated with the picture header may containintra coded slices and inter coded slices. The value of slice_types_idcmay be set equal to 2.

Note that when slice_types_idc has value equal to 2, it is stillpossible that the picture contains intra coded slices only or intercoded slices only.

d) Other values of slice_types_idc may be reserved for future use.

6. For slice_types_idc semantics in a picture header, the followingconstraints may be further specified.

a) When the picture associated with the picture header has one or moreintra coded slice, the value of slice_types_idc shall not be equal to 1.

b) When the picture associated with the picture header has one or moreinter coded slice, the value of slice_types_idc shall not be equal to 0.

7. slice_types_idc may be signaled in other parameter set such aspicture parameter set (PPS) instead of in picture header.

As an embodiment, the encoding apparatus and the decoding apparatus mayuse the following Table 2 and Table 3 as the syntax and semantics of thepicture header based on the methods of 1 and 2 as described above.

TABLE 2 Descriptor picture_header_rbsp( ) {  ... intra_signalling_present_flag  u (1)  inter_signalling_present_flag  u(1)  if( partition_constraints_override_enabled_flag ) {  partition_constraints_override_flag ue (v)   if(partition_constraints_override_flag ) {    if(intra_signalling_present_flag ) {    pic_log2_diff_min_qt_min_cb_intra_slice_luma ue (v)    pic_max_mtt_hierarchy_depth_intra_slice_luma ue (v)     if(pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {     pic_log2_diff_max_bt_min_qt_intra_slice_luma ue (v)     pic_log2_diff_max_tt_min_qt_intra_slice_luma ue (v)     }     if(qtbtt_dual_tree_intra_flag ) {     pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue (v)     pic_max_mtt_hierarchy_depth_intra_slice_chroma ue (v)      if(pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {      pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue (v)      pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue (v)      }     }   }    if( inter_signalling_present_flag ){    pic_log2_diff_min_qt_min_cb_inter_slice ue (v)    pic_max_mtt_hierarchy_depth_inter_slice ue (v)     if(pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {     pic_log2_diff_max_bt_min_qt_inter_slice ue (v)     pic_log2_diff_max_tt_min_qt_inter_slice ue (v)     }    }   }  } if( intra_signalling_present_flag ) {   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_intra_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_intra_slice ue (v)  }  if(inter_signalling_present_flag ){   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_inter_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_inter_slice ue (v)   if(sps_temporal_mvp_enabled_flag )    pic_temporal_mvp_enabled_flag  u (1)  if(!pps_mvd_l1_zero_idc )    mvd_l1_zero_flag  u (1)   if(!pps_six_minus_max_num_merge_cand_plus1 )   pic_six_minus_max_num_merge_cand ue (v)   if( sps_affine_enabled_flag)    pic_five_minus_max_num_subblock_merge_cand ue (v)   if(sps_fpel_mmvd_enabled_flag )    pic_fpel_mmvd_enabled_flag  u (1)   if(sps_bdof_pic_present_flag )    pic_disable_bdof_flag  u (1)   if(sps_dmvr_pic_present_flag )    pic_disable_dmvr_flag  u (1)   if(sps_prof_pic_present_flag )    pic_disable_prof_flag  u (1)   if(sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&    !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 )   pic_max_num_merge_cand_minus_max_num_triangle_cand ue (v)  }  if(sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue (v) if( sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag  u (1) if( sps_sao_enabled_flag ) {   pic_sao_enabled_present_flag  u (1)  if( pic_sao_enabled_present_flag ) {    pic_sao_luma_enabled_flag  u(1)    if( ChromaArrayType != 0 )     pic_sao_chroma_enabled_flag  u (1)  }  }  ... }

TABLE 3 intra_signalling_present_flag equal to 1 specifies that syntaxelemems used only by intra coded slices are present in the pictureheader. intra_signalling_present_flag equal to 0 specifies that syntaxelements used only by intra coded slices are not present in the pictureheader. It is a requirement of bitstream conformance that, the value ofintra_signalling_present_flag shall be equal to 1 when the pictureassociated with the picture header has one or more slice with slice_typeequal to 1. inter_signalling_present_flag equal to 1 specifies thatsyntax elements used only by inter coded slices are present in thepicture header, inter_signalling_present_flag equal to 0 specifies thatsyntax elements used only by inter coded slices are not present in thepicture header. It is a requirement of bitstream conformance that, thevalue of inter_signalling_present_flag shall be equal to 1 when thepicture associated with the picture header has one or more slice withslice_type equal to P or B. NOTE-: The values of bothintra_signalling_present_flag and inter_signalling_present_flag shouldbe set equal to 1 in the picture header associated with picturecontaining one or more subpicutres containing intra coded slice(s) whichmay be merged with one or inore subpicture(s) containing inter codedslices(s)

Referring to Table 2 and Table 3, if the value ofintra_signaling_present_flag is 1, this may represent that the syntaxelement being used only in the intra-coded slice is present in thepicture header. If the value of the intra_signaling_present_flag is 0,this may represent that the syntax element being used only in theintra-coded slice is not present in the picture header. Accordingly, ifthe picture related to the picture header includes one or more sliceshaving the slice type of I slice, the value of theintra_signaling_present_flag becomes 1. Further, if the picture relatedto the picture header does not include the slices having the slice typeof I slice, the value of the intra_signaling_present_flag becomes 0.

If the value of the inter_signaling_present_flag is 1, this mayrepresent that the syntax element being used only in the inter-codedslice is present in the picture header. If the value of theinter_signaling_present_flag is 0, this may represent that the syntaxelement being used only in the inter-coded slice is not present in thepicture header. Accordingly, if the picture related to the pictureheader includes one or more slices having the slice type of P sliceand/or B slice, the value of the intra_signaling_present_flag becomes 1.Further, if the picture related to the picture header does not includethe slices having the slice type of P slice and/or B slice, the value ofthe intra_signaling_present_flag becomes 0.

Further, in case of the picture including one or more subpicturesincluding the intra-coded slices which can be merged with one or moresubpictures including the inter-coded slices, both the value of theintra_signaling_present_flag and the value of theinter_signaling_present_flag are set to be 1.

For example, in case that only the inter-coded slices (P slice and/or Bslice) are included in the current picture, the encoding apparatus maydetermine the value of the inter_signaling_present_flag as 1, and thevalue of the intra_signaling_present_flag as 0.

As another example, in case that only the intra-coded slice (I slice) isincluded in the current picture, the encoding apparatus may determinethe value of the inter_signaling_present_flag as 0, and the value of theintra_signaling_present_flag as 1.

As still another example, in case that at least one inter-coded slice orat least one intra-coded slice is included in the current picture, theencoding apparatus may determine the value of theinter_signaling_present_flag and the value of theintra_signaling_present_flag as 1 in all.

In case that the value of the intra_signaling_present_flag is determinedas 0, the encoding apparatus may generate image information in which thesyntax elements necessary for the intra slice are excluded or omitted,and only the syntax elements necessary for the inter slice is includedin the picture header. If the value of the inter_signaling_present_flagis determined as 0, the encoding apparatus may generate the imageinformation in which the syntax elements necessary for the inter sliceare excluded or omitted, and only the syntax elements necessary for theintra slice is included in the picture header.

If the value of the inter_signaling_present_flag obtained from thepicture header in the image information is 1, the decoding apparatus maydetermine that at least one inter-coded slice is included in thecorresponding picture, and may parse the syntax elements necessary forthe intra prediction from the picture header. If the value of theinter_signaling_present_flag is 0, the decoding apparatus may determinethat only the intra-coded slice is included in the correspondingpicture, and may parse the syntax elements necessary for the intraprediction from the picture header. If the value of theintra_signaling_present_flag obtained from the picture header in theimage information is 1, the decoding apparatus may determine that atleast one intra-coded slice is included in the corresponding picture,and may parse the syntax elements necessary for the intra predictionfrom the picture header. If the value of theintra_signaling_present_flag is 0, the decoding apparatus may determinethat only the inter-coded slice is included in the correspondingpicture, and may parse the syntax elements necessary for the interprediction from the picture header.

As another embodiment, the encoding apparatus and the decoding apparatusmay use the following Table 4 and Table 5 as the syntax and semantics ofthe picture header based on the above methods of 5 and 6.

TABLE 4 Descriptor picture_header_rbsp( ) {  ...  slice_type_idc  u (1) if( partition_constraints_override_enabled_flag ) {  u (1)  partition_constraints_override_flag   if(partition_constraints_override_flag ) { ue (v)    if( slice_type_idc !=1 ) {     pic_log2_diff_min_qt_min_cb_intra_slice_luma ue (v)    pic_max_mtt_hierarchy_depth_intra_slice_luma ue (v)     if(pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {     pic_log2_diff_max_bt_min_qt_intra_slice_luma ue (v)     pic_log2_diff_max_tt_min_qt_intra_slice_luma ue (v)     }     if(qtbtt_dual_tree_intra_flag ) {     pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue (v)     pic_max_mtt_hierarchy_depth_intra_slice_chroma ue (v)      if(pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {      pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue (v)      pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue (v)      }     }   }    if( slice_type_idc != 0 ) {    pic_log2_diff_min_qt_min_cb_inter_slice ue (v)    pic_max_mtt_hierarchy_depth_inter_slice ue (v)     if(pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {     pic_log2_diff_max_bt_min_qt_inter_slice ue (v)     pic_log2_diff_max_tt_min_qt_inter_slice ue (v)     }    }   }  } if( slice_type_idc != 1 ) {   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_intra_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_intra_slice ue (v)  }  if(slice_type_idc != 0 ) {   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_inter_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_inter_slice ue (v)   if(sps_temporal_mvp_enabled_flag )    pic_temporal_mvp_enabled_flag  u (1)  if(!pps_mvd_l1_zero_idc )    mvd_l1_zero_flag  u (1)   if(!pps_six_minus_max_num_merge_cand_plus1 )   pic_six_minus_max_num_merge_cand ue (v)   if( sps_affine_enabled_flag)    pic_five_minus_max_num_subblock_merge_cand ue (v)   if(sps_fpel_mmvd_enabled_flag )    pic_fpel_mmvd_enabled_flag  u (1)   if(sps_bdof_pic_present_flag )    pic_disable_bdof_flag  u (1)   if(sps_dmvr_pic_present_flag )    pic_disable_dmvr_flag  u (1)   if(sps_prof_pic_present_flag )    pic_disable_prof_flag  u (1)   if(sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&    !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 )   pic_max_num_merge_cand_minus_max_num_triangle_cand ue (v)  }  if(sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue (v) if( sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag  u (1) if( sps_sao_enabled_flag ) {   pic_sao_enabled_present_flag  u (1)  if( pic_sao_enabled_present_flag ) {   pic_sao_luma_enabled_present_flag  u (1)    if( ChromaArrayType != 0)     pic_sao_chroma_enabled_flag  u (1) }  }  ... }

TABLE 5 slice_types_idc equal to 0 specifies that all slices of thepicture associated with the picture header are I slices. slice_types_idcequal to 1 specifies that all slices of the picture associated with thepicture header are either P or B slices. slice_types_idc equal to 2specifics that slices of the picture associatcd with the picture headermay be I, P, and/ or B slices, The value slice_types_idc equal to 3 isreserved. It is a requirement of bitstrearn conformance that, the valueof slice_types_idc equal to shall be not be equal to either 0 or 1 whenthe picture associated with the picture header has intra coded slice(s)and inter coded slice(s) NOTE-: The value slice_types_idc should be setequal to 2 in the picture header associated with picture containing oneor more subpictures containing intra coded slice(s) which may be mergedwith ono or more subpicture(s) containing inter coded slice(s)

Referring to Table 4 and Table 5, if the value of slice_types_idc is 0,this represents that the type of all slices in the picture related tothe picture header is I slice. If the value of the slice_types_idc is 1,this represents that the type of all slices in the picture related tothe picture header is P or B slice. If the value of the slice_types_idcis 2, this represents that the slice type of the slices in the picturerelated to the picture header is I, P, and/or B slice.

For example, if only the intra-coded slice is included in the currentpicture, the encoding apparatus may determine the value of theslice_types_idc as 0, and may include only the syntax elements necessaryfor decoding of the intra slice in the picture header. That is, in thiscase, the syntax elements necessary for the inter slice are not includedin the picture header.

As another example, if only the inter-coded slice is included in thecurrent picture, the encoding apparatus may determine the value of theslice_types_idc as 1, and may include only the syntax elements necessaryfor decoding of the inter slice in the picture header. That is, in thiscase, the syntax elements necessary for the intra slice are not includedin the picture header.

As still another example, if at least one inter-coded slice and at leastone intra-coded slice are included in the current picture, the encodingapparatus may determine the value of the slice_types_idc as 2, and mayinclude all of the syntax elements necessary for the decoding of theinter slice and the syntax elements necessary for the decoding of theintra slice in the picture header.

If the value of the slice_types_idc obtained from the picture header inthe image information is 0, the decoding apparatus may determine thatonly the intra-coded slice is included in the corresponding picture, andmay parse the syntax elements necessary for the decoding of theintra-coded slice from the picture header. If the value of theslice_types_idc is 1, the decoding apparatus may determine that only theinter-coded slice is included in the corresponding picture, and mayparse the syntax elements necessary for the decoding of the inter-codedslice from the picture header. If the value of the slice_types_idc is 2,the decoding apparatus may determine that at least one intra-coded sliceand at least one inter-coded slice are included in the correspondingpicture, and may parse the syntax elements necessary for the decoding ofthe intra-coded slice and the syntax elements necessary for the decodingof the inter-coded slice from the picture header.

As still another embodiment, the encoding apparatus and the decodingapparatus may use one flag representing whether the picture includes theintra- and inter-coded slices. If the flag is true, that is, if thevalue of the flag is 1, all of the intra slice and the inter slice maybe included in the corresponding picture. In this case, the followingTable 6 and Table 7 may be used as the syntax and the semantics of thepicture header.

TABLE 6 Descriptor picture_header_rbsp( ) {  ... mixed_slice_signalling_present_flag  u (1)  if(mixed_slice_signalling_present_flag   intra_slice_only_flag  u (1)  if(partition_constraints_override_enabled_flag ) {  partition_constraints_override_flag ue (v)   if(partition_constraints_override_flag ) {   if(IntraSignallingPresentFlag){    pic_log2_diff_min_qt_min_cb_intra_slice_luma ue (v)    pic_max_mtt_hierarchy_depth_intra_slice_luma ue (v)     if(pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) {     pic_log2_diff_max_bt_min_qt_intra_slice_luma ue (v)     pic_log2_diff_max_tt_min_qt_intra_slice_luma ue (v)     }     if(qtbtt_dual_tree_intra_flag ) {     pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue (v)     pic_max_mtt_hierarchy_depth_intra_slice_chroma ue (v)      if(pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) {      pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue (v)      pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue (v)      }     }   }    if(IntraSignallingPresentFlag){    pic_log2_diff_min_qt_min_cb_inter_slice ue (v)    pic_max_mtt_hierarchy_depth_inter_slice ue (v)     if(pic_max_mtt_hierarchy_depth_inter_slice != 0 ) {     pic_log2_diff_max_bt_min_qt_inter_slice ue (v)     pic_log2_diff_max_tt_min_qt_inter_slice ue (v)     }    }   }  } if(IntraSignallingPresentFlag){   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_intra_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_intra_slice ue (v)  } if(InterSignallingPresentFlag){   if( cu_qp_delta_enabled_flag )   pic_cu_qp_delta_subdiv_inter_slice ue (v)   if(pps_cu_chroma_qp_offset_list_enabled_flag )   pic_cu_chroma_qp_offset_subdiv_inter_slice ue (v)   if(sps_temporal_mvp_enabled_flag )    pic_temporal_mvp_enabled_flag  u (1)  if(!pps_mvd_l1_zero_idc )    mvd_l1_zero_flag  u (1)   if(!pps_six_minus_max_num_merge_cand_plus1 )   pic_six_minus_max_num_merge_cand ue (v)   if( sps_affine_enabled_flag)    pic_five_minus_max_num_subblock_merge_cand ue (v)   if(sps_fpel_mmvd_enabled_flag )    pic_fpel_mmvd_enabled_flag  u (1)   if(sps_bdof_pic_present_flag )    pic_disable_bdof_flag  u (1)   if(sps_dmvr_pic_present_flag )    pic_disable_dmvr_flag  u (1)   if(sps_prof_pic_present_flag )    pic_disable_prof_flag  u (1)   if(sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&    !pps_max_num_merge_cand_minus_max_num_triangle_cand_minus1 )   pic_max_num_merge_cand_minus_max_num_triangle_cand ue (v)  }  if(sps_ibc_enabled_flag )   pic_six_minus_max_num_ibc_merge_cand ue (v) if( sps_joint_cbcr_enabled_flag )   pic_joint_cbcr_sign_flag  u (1) if( sps_sao_enabled_flag ) {   pic_sao_enabled_present_flag  u (1)  if( pic_sao_enabled_present_flag ) {    pic_sao_luma_enabled_flag  u(1)    if( ChromaArrayType != 0 )     pic_sao_chroma_enabled_flag  u (1)  }  }  ... }

TABLE 7 mixed_slice_signalling_present_flag equal to 1 specifies thatthe picture associated with the picture header may have one or moreslices with different types. mixed_slice_signalling_present_flag equalto 0 specifies that the picture associated with the picture headercontains data pertaining to only a single slice type. The variablesInterSignallingPresentFlag and IntraSignallingPresentFlag are defined tospecifiy whether syntax elements needed by intra coded slices and syntaxelements needed by inter coded slices respectively, are present in thepicture or not. When mixed_slice_signalling_present_flag is equal to 1,IntraSignallingPresentFlag and InterSignallingPresentFlag are set to beequal to 1. intra_slice_only_flag equal to 1 specifies that the value ofIntraSignallingPresentFlag is set to be equal to 1 and the value ofInterSignallingPresentFlag is set to be equal to 0.intra_slice_only_flag equal to 0 specifies thatIntraSignallingPresentFlag is set equal to 0 and the value ofInterSignallingPresentFlag is set equal to 1. It is a requirement ofbitstream conformance that, the value of IntraSignallingPresentFlagshall be equal to 1 when the picture associated with the picture headerhas one or more slice with slice_type equal to I. It is a requirement ofbitstream conformance that, the value of InterSignallingPresentFlagshall be equal to 1 when the picture associated with the picture headerhas one or more slice with slice_type equal to P or B. NOTE-: The valuesof both intra_signalling_present_flag and inter_signalling_present_flagshould be set equal to 1 in the picture header assciated with picturecontaining one or more subpictures containing intra coded slice(s) whichmay be merged with one or more subpicture(s) containing inter codedslice(s)

Referring to Table 6 and Table 7, if the value ofmixed_slice_signaling_present_flag is 1, this may represent that thepicture related to the corresponding picture header has one or moreslices having different types. If the value of themixed_slice_signaling_present_flag is 0, this may mean that the picturerelated to the corresponding picture header includes data related toonly a single slice type.

Variables InterSignalingPresentFlag and IntraSignalingPresentFlagrepresent whether the syntax element necessary for the intra-coded sliceand the syntax element necessary for the inter-coded slice are presentin the corresponding picture header, respectively. If the value of themixed_slice_signaling_present_flag is 1, the values of theIntraSignalingPresentFlag and the InterSignalingPresentFlag are set to1.

If the value of intra_slice_only_flag is set to 1, it represents thatthe value of IntraSignalingPresentFlag is set to 1, and the value of theInterSignalingPresentFlag is set to 0. If the value of theintra_slice_only_flag is 0, it represents that the value of theIntraSignalingPresentFlag is set to 0, and the value of theInterSignalingPresentFlag is set to 1.

If the picture related to the picture header has one or more sliceshaving the slice type of I slice, the value of theIntraSignalingPresentFlag is set to 1. If the picture related to thepicture header has one or more slices having the slice type of P or Bslice, the value of the InterSignalingPresentFlag is set to 1.

For example, if only the intra-coded slice is included in the currentpicture, the encoding apparatus may determine the value ofmixed_slice_signaling_present_flag as 0, may determine the value ofintra_slice_only_flag as 1, may determine the value ofIntraSignalingPresentFlag as 1, and may determine the value ofInterSignalingPresentFlag as 0.

As another example, if only the inter-coded slice is included in thecurrent picture, the encoding apparatus may determine the value of themixed_slice_signaling_present_flag as 0, may determine the value of theintra_slice_only_flag as 0, may determine the value of theIntraSignalingPresentFlag as 0, and may determine the value of theInterSignalingPresentFlag as 1.

As still another example, if at least one intra-coded slice and at leastone inter-coded slice are included in the current picture, the encodingapparatus may determine the values of themixed_slice_signaling_present_flag, the IntraSignalingPresentFlag, andthe InterSignalingPresentFlag as 1, respectively.

If the value of the mixed_slice_signaling_present_flag obtained from thepicture header in the image information is 0, the decoding apparatus maydetermine that only the intra-coded slice or inter-coded slice isincluded in the corresponding picture. In this case, if the value of theintra_slice_only_flag obtained from the picture header is 0, thedecoding apparatus may parse only the syntax elements necessary fordecoding of the inter-coded slice from the picture header. If the valueof the intra_slice_only_flag is 1, the decoding apparatus may parse onlythe syntax element necessary for decoding of the intra-coded slice fromthe picture header.

If the value of the mixed_slice_signaling_present_flag obtained from thepicture header in the image information is 1, the decoding apparatus maydetermine that at least one intra-coded slice and at least oneinter-coded slice are included in the corresponding picture, and mayparse the syntax elements necessary for the decoding of the inter-codedslice and the syntax elements necessary for the decoding of theintra-coded slice from the picture header.

FIGS. 10 and 11 schematically represent an example of a video/imageencoding method and associated components according to an embodiment ofthis document.

The video/image encoding method disclosed in FIG. 10 may be performed bythe (video/image) encoding apparatus 200 disclosed in FIGS. 2 and 11 .Specifically, for example, S1000 of FIG. 10 may be performed by thepredictor 220 of the encoding apparatus 200; S1010 may be performed bythe entropy encoder 240 of the encoding apparatus 200; and S1020 may beperformed by the residual processor 230 of the encoding apparatus 200.S1030 may be performed by the entropy encoder 240 of the encodingapparatus 200. The video/image encoding method disclosed in FIG. 10 mayinclude the embodiments described above in this document.

Specifically, referring to FIGS. 8 and 9 , the predictor 220 of theencoding apparatus may determine the prediction mode of the currentblock in the current picture. The current picture may include aplurality of slices. The predictor 220 of the encoding apparatus maygenerate prediction samples (predicted block) for the current blockbased on the prediction mode (S1000). Here, the prediction mode mayinclude an inter prediction mode and an intra prediction mode. When theprediction mode of the current block is the inter prediction mode, theprediction samples may be generated by the inter predictor 221 of thepredictor 220. When the prediction mode of the current block is theintra prediction mode, the prediction samples may be generated by theintra predictor 222 of the predictor 220.

Meanwhile, the residual processor 230 of the encoding apparatus maygenerate a residual sample and residual information based on theprediction samples and an original picture (original block, originalsamples) (S1020). Here, the residual information is information aboutthe residual samples, and may include information about (quantized)transform coefficients for the residual samples.

The adder (or reconstructor) of the encoding apparatus may generatereconstructed samples (reconstructed picture, reconstructed block,reconstructed sample array) by adding the residual samples generated bythe residual processor 230 and the prediction samples generated by theinter predictor 221 or the intra predictor 222.

The entropy encoder 240 of the encoding apparatus may generate at leastone of the first information indicating whether information necessaryfor an inter prediction operation for a decoding process based on theprediction mode is present in a picture header associated with thecurrent picture, or the second information indicating whetherinformation necessary for an intra prediction operation for the decodingprocess is present in a picture header associated with the currentpicture (S1010). Here, the first information and the second informationare information included in the picture header of the image information,and may correspond to the aforementioned intra_signalling_present_flag,inter_signalling_present_flag, slice_type_idc,mixed_slice_signalling_present_flag, intra_slice_only_flag,IntraSignallingPresentFlag and/or InterSignallingPresentFlag.

As an example, in case that the information necessary for the interprediction operation for the decoding process is included in the pictureheader related to the current picture as the inter-coded slice isincluded in the current picture, the entropy encoder 240 of the encodingapparatus may determine the value of the first information as 1.Further, in case that the information necessary for the intra predictionoperation for the decoding process is included in the correspondingpicture header as the intra-coded slice is included in the currentpicture, the entropy encoder 240 of the encoding apparatus may determinethe value of the second information as 1. In this case, the firstinformation may correspond to the inter_signaling_present_flag, and thesecond information may correspond to the intra_signaling_present_flag.The first information may be called a first flag, information on whethersyntax elements being used for inter slices are present in the pictureheader, a flag for whether syntax elements being used for the interslices are present in the picture header, information on whether slicesin the current picture are inter slices, or a flag for whether theslices are inter slices. The second information may be called a secondflag, information on whether syntax elements being used for intra slicesare present in the picture header, a flag for whether syntax elementsbeing used for the intra slices are present in the picture header,information on whether slices in the current picture are intra slices,or a flag for whether the slices are intra slices.

Meanwhile, in case that only the information necessary for the intraprediction operation is included in the corresponding picture header asonly the intra-coded slice is included in the picture, the entropyencoder 240 of the encoding apparatus may determine the value of thefirst information as 0, and may determine the value of the secondinformation as 1. Further, in case that only the information necessaryfor the inter prediction operation is included in the correspondingpicture header as only the inter-coded slice is included in the picture,the value of the first information may be determined as 1, and the valueof the second information may be determined as 0. Accordingly, if thevalue of the first information is 0, all slices in the current picturemay have I slice type. If the value of the second information is 0, allthe slices in the current picture may have the P slice type or the Bslice type. Here, the information necessary for the intra predictionoperation may include the syntax element being used for decoding of theintra slice, and the information necessary for the inter predictionoperation may include the syntax element being used for decoding of theinter slice.

As another example, if all the slices in the current picture have the Islice type, the entropy encoder 240 of the encoding apparatus maydetermine the value of the information about the slice type as 0, and ifall the slices in the current picture have the P slice type or the Bslice type, the entropy encoder 240 of the encoding apparatus maydetermine the value of the information about the slice type as 1. If allthe slices in the current picture have I slice type, P slice type,and/or B slice type (i.e., the slice types of the slices in the pictureare mixed), the entropy encoder 240 of the encoding apparatus maydetermine the value of the information about the slice type as 2. Inthis case, the information about the slice type may correspond to theslice_type_idc.

As still another example, if all the slices in the current picture havethe same slice type, the entropy encoder 240 of the encoding apparatusmay determine the value of the information about the slice type as 0,and if the slices in the current picture have different slice types, theentropy encoder 240 of the encoding apparatus may determine the value ofthe information about the slice type as 1. In this case, the informationabout the slice type may correspond to themixed_slice_signaling_present_flag.

If the value of the information about the slice type is determined as 0,information on whether the intra slice is included in the slices may beincluded in the corresponding picture header. The information on whetherthe intra slice is included in the slices may correspond to theintra_slice_only_flag. If all the slices in the picture have the I slicetype, the entropy encoder 240 of the encoding apparatus may determinethe value of the information on whether the intra slice is included inthe slices as 1, determine the value of the information on whether thesyntax elements being used for the intra slice are present in thepicture header as 1, and determine the value of the information onwhether the syntax elements being used for the inter slice is present inthe picture header as 0. If the slice type of all the slices in thepicture is the P slice and/or B slice type, the entropy encoder 240 ofthe encoding apparatus may determine the value of the information onwhether the intra slice is included in the slices as 0, determine thevalue of the information on whether the syntax elements being used forthe intra slice are present in the picture header as 0, and determinethe value of the information on whether the syntax elements being usedfor the inter slice is present in the picture header as 1.

The entropy encoder 240 of the encoding apparatus may encode imageinformation including the above-described first information, secondinformation, and slice type information along with residual information,prediction-related information and the like (S1030). For example, theimage information may include the partitioning-related information,information on the prediction mode, residual information, in-loopfiltering-related information, first information, second information,information about a slice type, and the like, and include various syntaxelements related to them. In an example, the image information mayinclude information on various parameter sets such as an adaptationparameter set (APS), a picture parameter set (PPS), a sequence parameterset (SPS), a video parameter set (VPS) or the like. In addition, theimage information may include various informations such as pictureheader syntax, picture header structure syntax, slice header syntax,coding unit syntax, and the like. The above-described first information,second information, information about a slice type, informationnecessary for the intra prediction operation, and information necessaryfor the inter prediction operation may be included in the syntax in thepicture header.

Information encoded by the entropy encoder 240 of the encoding apparatusmay be output in the form of a bitstream. The bitstream may betransmitted to the decoding apparatus through a network or a storagemedium.

FIGS. 12 and 13 schematically represent an example of a video/imagedecoding method and associated components according to an embodiment ofthis document.

The video/image decoding method disclosed in FIG. 12 may be performed bythe (video/image) decoding apparatus 300 disclosed in FIGS. 3 and 13 .Specifically, for example, S1200 and S1210 of FIG. 12 may be performedin the entropy decoder 310 of the decoding apparatus, and S1220 may beperformed in the predictor 330 of the decoding apparatus 300. S1230 maybe performed by the residual processor 320 of the decoding apparatus300, and S1240 may be performed by the adder 340 of the decodingapparatus 300. The video/image decoding method disclosed in FIG. 12 mayinclude the embodiments described above in this document.

Referring to FIGS. 12 and 13 , the entropy decoder 310 of the decodingapparatus may obtain image information from a bitstream (S1200). Theimage information may include a picture header associated with thecurrent picture. The current picture may include a plurality of slices.

Meanwhile, the entropy decoder 310 of the decoding apparatus may obtainor parse, based on the picture header, at least one of the first flagindicating whether information necessary for an inter predictionoperation for a decoding process is present in a picture headerassociated with the current picture, or the second flag indicatingwhether information necessary for an intra prediction operation for thedecoding process is present in a picture header associated with thecurrent picture (S1210). Here, the first flag and the second flag maycorrespond to the aforementioned intra_signalling_present_flag,inter_signalling_present_flag, slice_type_idc,mixed_slice_signalling_present_flag, intra_slice_only_flag,IntraSignallingPresentFlag and/or InterSignallingPresentFlag. Theentropy decoder 310 of the decoding apparatus may parse the syntaxelements included in the picture header of the image information basedon the picture header syntax of any one of Tables 2, 4, and 6 describedabove.

The decoding apparatus may generate prediction samples by performing atleast one of intra prediction and inter prediction on the current blockin the current picture based on the first flag, the second flag,information about the slice type or the like (S1220).

Specifically, the entropy decoder 310 of the decoding apparatus mayparse (or obtain) at least one of the information necessary for theintra prediction operation and or the information necessary for theinter prediction operation for the decoding process from the pictureheader related to the current picture based on the first flag, thesecond flag, and/or the information about the slice type. The predictor330 of the decoding apparatus may generate prediction samples byperforming intra prediction and/or inter prediction based on at leastone of the information necessary for the intra prediction operation orthe information for the inter prediction. Here, the informationnecessary for the intra prediction operation may include a syntaxelement being used for decoding of an intra slice, and the informationnecessary for the inter prediction operation may include a syntaxelement being used for decoding of an inter slice.

As an example, if the value of the first flag is 0, the entropy decoder310 of the decoding apparatus may determine (or decide) that the syntaxelements being used for the inter prediction are not present in thepicture header, and may parse only the information necessary for theintra prediction operation from the picture header. If the value of thefirst flag is 1, the entropy decoder 310 of the decoding apparatus maydetermine (or decide) that the syntax elements being used for the interprediction are present in the picture header, and may parse theinformation necessary for the inter prediction operation from thepicture header. In this case, the first flag may correspond to theinter_signaling_present_flag.

Further, if the value of the second flag is 0, the entropy decoder 310of the decoding apparatus may determine (or decide) that the syntaxelements being used for the intra prediction are not present in thepicture header, and may parse only the information necessary for theinter prediction operation from the picture header. If the value of thesecond flag is 1, the entropy decoder 310 of the decoding apparatus maydetermine (or decide) that the syntax elements being used for the intraprediction are present in the picture header, and may parse theinformation necessary for the intra prediction operation from thepicture header. In this case, the second flag may correspond to theintra_signaling_present_flag.

If the value of the first flag is 0, the decoding apparatus maydetermine that all slices in the current picture have the type of Islice. If the value of the first flag is 1, the decoding apparatus maydetermine that 0 or more slices in the current picture have the type ofP slice or B slice. In other words, if the value of the first flag is 1,the slice having the type of P slice or B slice may be included or maynot be included in the current picture.

Further, if the value of the second flag is 0, the decoding apparatusmay determine that all slices in the current picture have the type of Pslice or B slice. If the value of the second flag is 1, the decodingapparatus may determine that 0 or more slices in the current picturehave the type of I slice. In other words, if the value of the secondflag is 1, the slice having the type of I slice may be included or maynot be included in the current picture.

As another example, if the value of the information about the slice typeis 0, the entropy decoder 310 of the decoding apparatus may determinethat all slices in the current picture have I slice type, and may parseonly the information necessary for the intra prediction operation. Ifthe information about the slice type is 1, the entropy decoder 310 ofthe decoding apparatus may determine that all slices in thecorresponding picture have the P slice type or the B slice type, and mayparse only the information necessary for the inter prediction operationfrom the picture header. If the value of the information for the slicetype is 2, the entropy decoder 310 of the decoding apparatus maydetermine that the slices in the corresponding picture have the slicetype in which the I slice type, the P slice type, and/or the B slicetype are mixed, and may parse all of the information necessary for theinter prediction operation and the information necessary for the intraprediction operation from the picture header. In this case, theinformation about the slice type may correspond to the slice_type_idc.

As still another example, the entropy decoder 310 of the decodingapparatus may determine that all slices in the current picture have thesame slice type if the value of the information about the slice type isdetermined as 0, and may determine that slices in the current picturehave different slice types if the value of the information about theslice type is determined as 1. In this case, the information about theslice type may correspond to the mixed_slice_signalling_present_flag.

If the value of the information about the slice type is determined as 0,the entropy decoder 310 of the decoding apparatus may parse informationon whether the intra slice is included in the slices from the pictureheader. The information on whether the intra slice is included in theslices may correspond to the intra_slice_only_flag as described above.If the information on whether the intra slice is included in the slicesis 1, all the slices in the picture may have I slice type.

If the value of the information on whether the intra slice is includedin the slices is 1, the entropy decoder 310 of the encoding apparatusmay parse only the information necessary for the intra predictionoperation from the picture header. If the value of the information onwhether the intra slice is included in the slices is 0, the entropydecoder 310 of the decoding apparatus may parse only the informationnecessary for the inter prediction operation from the picture header.

If the value of the information about the slice type is 1, the entropydecoder 310 of the decoding apparatus may parse all of the informationnecessary for the inter prediction operation and the informationnecessary for the intra prediction operation from the picture header.

Meanwhile, the residual processor 320 of the decoding apparatus maygenerate residual samples based on the residual information obtainedfrom the image information by the entropy decoder 310 (S1230).

The adder 340 of the decoding apparatus may generate reconstructedsamples based on the prediction samples generated by the predictor 330and the residual samples generated by the residual processor 320(S1240). In addition, the adder 340 of the decoding apparatus maygenerate a reconstructed picture (reconstructed block) based on thereconstructed samples.

After this, an in-loop filtering procedure such as an ALF procedure, SAOand/or deblocking filtering may be applied as needed to thereconstructed picture in order to improve subjective/objective videoquality.

Although methods have been described on the basis of a flowchart inwhich steps or blocks are listed in sequence in the above-describedembodiments, the steps of the present disclosure are not limited to acertain order, and a certain step may be performed in a different stepor in a different order or concurrently with respect to that describedabove. Further, it will be understood by those ordinary skilled in theart that the steps of the flowcharts are not exclusive, and another stepmay be included therein or one or more steps in the flowchart may bedeleted without exerting an influence on the scope of the presentdisclosure.

The aforementioned method according to the present disclosure may be inthe form of software, and the encoding apparatus and/or decodingapparatus according to the present disclosure may be included in adevice for performing image processing, for example, a TV, a computer, asmart phone, a set-top box, a display device, or the like.

When the embodiments of the present disclosure are implemented bysoftware, the aforementioned method may be implemented by a module(process or function) which performs the aforementioned function. Themodule may be stored in a memory and executed by a processor. The memorymay be installed inside or outside the processor and may be connected tothe processor via various well-known means. The processor may includeApplication-Specific Integrated Circuit (ASIC), other chipsets, alogical circuit, and/or a data processing device. The memory may includea Read-Only Memory (ROM), a Random Access Memory (RAM), a flash memory,a memory card, a storage medium, and/or other storage device. In otherwords, the embodiments according to the present disclosure may beimplemented and executed on a processor, a micro-processor, acontroller, or a chip. For example, functional units illustrated in therespective figures may be implemented and executed on a computer, aprocessor, a microprocessor, a controller, or a chip. In this case,information on implementation (for example, information on instructions)or algorithms may be stored in a digital storage medium.

In addition, the decoding apparatus and the encoding apparatus to whichthe embodiment(s) of the present disclosure is applied may be includedin a multimedia broadcasting transceiver, a mobile communicationterminal, a home cinema video device, a digital cinema video device, asurveillance camera, a video chat device, and a real time communicationdevice such as video communication, a mobile streaming device, a storagemedium, a camcorder, a video on demand (VoD) service provider, an OverThe Top (OTT) video device, an internet streaming service provider, a 3Dvideo device, a Virtual Reality (VR) device, an Augment Reality (AR)device, an image telephone video device, a vehicle terminal (forexample, a vehicle (including an autonomous vehicle) terminal, anairplane terminal, or a ship terminal), and a medical video device; andmay be used to process an image signal or data. For example, the OTTvideo device may include a game console, a Bluray player, anInternet-connected TV, a home theater system, a smartphone, a tablet PC,and a Digital Video Recorder (DVR).

In addition, the processing method to which the embodiment(s) of thepresent disclosure is applied may be produced in the form of a programexecuted by a computer and may be stored in a computer-readablerecording medium. Multimedia data having a data structure according tothe embodiment(s) of the present disclosure may also be stored in thecomputer-readable recording medium. The computer readable recordingmedium includes all kinds of storage devices and distributed storagedevices in which computer readable data is stored. The computer-readablerecording medium may include, for example, a Bluray disc (BD), auniversal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, aCD-ROM, a magnetic tape, a floppy disk, and an optical data storagedevice. The computer-readable recording medium also includes mediaembodied in the form of a carrier wave (for example, transmission overthe Internet). In addition, a bitstream generated by the encoding methodmay be stored in the computer-readable recording medium or transmittedthrough a wired or wireless communication network.

In addition, the embodiment(s) of the present disclosure may be embodiedas a computer program product based on a program code, and the programcode may be executed on a computer according to the embodiment(s) of thepresent disclosure. The program code may be stored on acomputer-readable carrier.

FIG. 14 represents an example of a contents streaming system to whichthe embodiment of the present disclosure may be applied.

Referring to FIG. 14 , the content streaming system to which theembodiments of the present disclosure is applied may generally includean encoding server, a streaming server, a web server, a media storage, auser device, and a multimedia input device.

The encoding server functions to compress to digital data the contentsinput from the multimedia input devices, such as the smart phone, thecamera, the camcorder and the like, to generate a bitstream, and totransmit it to the streaming server. As another example, in a case inwhich the multimedia input device, such as, the smart phone, the camera,the camcorder or the like, directly generates a bitstream, the encodingserver may be omitted.

The bitstream may be generated by an encoding method or a bitstreamgeneration method to which the embodiments of the present disclosure isapplied. And the streaming server may temporarily store the bitstream ina process of transmitting or receiving the bitstream.

The streaming server transmits multimedia data to the user equipment onthe basis of a user's request through the web server, which functions asan instrument that informs a user of what service there is. When theuser requests a service which the user wants, the web server transfersthe request to the streaming server, and the streaming server transmitsmultimedia data to the user. In this regard, the contents streamingsystem may include a separate control server, and in this case, thecontrol server functions to control commands/responses betweenrespective equipment in the content streaming system.

The streaming server may receive contents from the media storage and/orthe encoding server. For example, in a case the contents are receivedfrom the encoding server, the contents may be received in real time. Inthis case, the streaming server may store the bitstream for apredetermined period of time to provide the streaming service smoothly.

For example, the user equipment may include a mobile phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personaldigital assistant (PDA), a portable multimedia player (PMP), anavigation, a slate PC, a tablet PC, an ultrabook, a wearable device(e.g., a watch-type terminal (smart watch), a glass-type terminal (smartglass), a head mounted display (HMD)), a digital TV, a desktop computer,a digital signage or the like.

Each of servers in the contents streaming system may be operated as adistributed server, and in this case, data received by each server maybe processed in distributed manner.

What is claimed is:
 1. A video decoding method performed by a videodecoding apparatus, the method comprising: receiving a bitstream,wherein the bitstream comprises image information, wherein the imageinformation includes a picture header associated with a current picture,and the image information includes residual information; deriving slicesof the current picture; obtaining, based on the picture header, firstflag information related to whether information for an inter slice ispresent in the picture header and second flag information related towhether information for an intra slice is present in the picture header;deriving prediction samples for blocks in the slices in the currentpicture based on the first flag information and the second flaginformation by performing at least one of intra prediction or interprediction; deriving residual samples based on the residual information;and generating reconstructed samples based on the prediction samples andthe residual samples, wherein the first flag information and the secondflag information are comprised in the picture header of the imageinformation.
 2. The method of claim 1, wherein syntax elements relatedto the inter slice are obtained in the picture header based on a valueof the first flag information being
 1. 3. The method of claim 1, whereinslices in the current picture have an I slice type based on a value ofthe first flag information being
 0. 4. The method of claim 1, wherein 0or more slices in the current picture have a P slice type or B slicetype based on a value of the first flag information being
 1. 5. Themethod of claim 1, wherein syntax elements related to the intra sliceare obtained in the picture header based on a value of the second flaginformation being
 1. 6. The method of claim 1, wherein slices in thecurrent picture have a P slice type or B slice type based on a value ofthe second flag information being
 0. 7. The method of claim 1, wherein 0or more slices in the current picture have an I slice type based on avalue of the first flag information being
 1. 8. A video encoding methodperformed by a video encoding apparatus, the method comprising: derivingslices of a current picture; generating prediction samples for a currentblock in a slice in current picture based on a prediction mode of thecurrent block in the current picture; generating first flag informationrelated to whether information for an inter slice is present in apicture header associated with the current picture or second flaginformation related to whether information for an intra slice is presentin the picture header; generating residual information based on theprediction samples; and encoding image information including the firstflag information, the second flag information and the residualinformation, wherein the first flag information and the second flaginformation are comprised in the picture header of the imageinformation.
 9. The method of claim 8, wherein a value of the first flaginformation is 0 based on slices in the current picture having an Islice type.
 10. The method of claim 8, wherein a value of the first flaginformation is 1 based on 0 or more slices in the current picture havinga P slice type or a B slice type.
 11. The method of claim 8, wherein avalue of the second flag information is 0 based on slices in the currentpicture having a P slice type or a B slice type.
 12. The method of claim8, wherein a value of the first flag information is 1 based on 0 or moreslices in the current picture having an I slice type.
 13. Anon-transitory computer-readable digital storage medium storing abitstream generated by a video encoding method, the method comprising:deriving slices of a current picture; generating prediction samples fora current block in a slice in the current picture based on a predictionmode of the current block in the current picture; generating first flaginformation related to whether information for an inter slice is presentin a picture header associated with the current picture or second flaginformation related to whether information for an intra slice is presentin the picture header; generating residual information based on theprediction samples; and encoding image information to generate thebitstream, wherein the image information includes the first flaginformation, the second flag information and the residual information,wherein the first flag information and the second flag information arecomprised in the picture header of the image information.